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//~ while (clock()<=69*CLOCKS_PER_SEC)
//~ #pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O3")
//~ #pragma GCC optimize("Ofast")
//~ #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//~ #pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>

using namespace std;

using ll=long long;
using ld=long double;
using pii=pair<int, int>;
using pll=pair<ll, ll>;
using vi=vector<int>;
using vll=vector<ll>;

template<class TH> void _dbg(const char *sdbg, TH h){ cerr<<sdbg<<" = "<<h<<endl; }
#ifdef LOCAL
#define _upgrade ios_base::sync_with_stdio(0);
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__);
#else
#define _upgrade ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define debug(...) 98;
#define cerr if(0) cout
#endif

#define pb push_back
#define mp make_pair
#define all(x) x.begin(),x.end()
#define sz(x) ((int)(x).size())
#define fi first
#define se second

#define erase_duplicates(x) sort(all(x)), (x).resize(distance((x).begin(), unique(all(x))));

#define watch(x) cout << (#x) << " is " << (x) << endl;

#define pow2(x) ((x)*(x))
#define mod(x, m) ((((x) % (m)) + (m)) % (m))
#define max3(a, b, c) max(a, max(b, c))
#define min3(a, b, c) min(a, min(b, c))

#define REP(i, a, b) for(int i = a; i <= b; ++i)
#define REPV(i, b, a) for(int i = b; i >= a; --i)

const double m_pi = acos(-1.0);
const int int_max = 0x3f3f3f3f;
const int M7 = 1000*1000*1000+7;
const int M9 = 1000*1000*1000+9;

vector<int> emptyvi;
vector<vector<int> > tab;
vector<vector<int> > tab2;

int main() {
    _upgrade
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    cout<<fixed<<setprecision(15);
    
    int n, m;cin>>n>>m;
    int parz = 0;
    int numPion = 0;
    int planszSize = n*m;

    REP(i,0,n-1){
        string s; cin>>s;
        tab.pb(emptyvi);
        REP(j, 0, m-1) {
            if(s[j] == '.') tab[i].pb(0);
            if(s[j] == 'O') {
                tab[i].pb(1);
                parz += i + j;
                ++numPion;
            }
        }
    }

    int parz2 = 0;
    REP(i,0,n-1){
        string s; cin>>s;
        tab2.pb(emptyvi);
        REP(j, 0, m-1) {
            if(s[j] == '.') tab2[i].pb(0);
            if(s[j] == 'O') {
                tab2[i].pb(1);
                parz2 += i + j;
            }
        }
    }

    if(parz%2 != parz2%2) {
        cout <<0<<"\n";
        return 0;
    }
    if(planszSize == 1) {
        cout <<1<<"\n";
        return 0;
    }

    long double myKraw=0;
    REP(i,0,n-1){
        REP(j, 0, m-1) {
            if(tab2[i][j]){
                if(i > 0 && !tab2[i-1][j])++myKraw;
                if(j > 0 && !tab2[i][j-1])++myKraw;
                if(i < n-1 && !tab2[i+1][j])++myKraw;
                if(j < m-1 && !tab2[i][j+1])++myKraw;
            }
        }
    }

    long double allPos = 1;

    int one =min(planszSize-numPion, numPion);
    int two =max(planszSize-numPion, numPion);

    REP(i, two+1, planszSize) {
        allPos*=i;
    }
    REP(i, 1, one) {
        allPos/=i;
    }

    long double allKraw = allPos * 4 * numPion;

    long double dimenKraw = allPos * 2 * numPion;

    long double krawPosn = dimenKraw / n;
    long double krawPosm = dimenKraw / m;

    long double otherPosn = dimenKraw * (n-1)*(numPion-1) / n / (planszSize-1);
    long double otherPosm = dimenKraw * (m-1)*(numPion-1) / m / (planszSize-1);

    long double existing = allKraw - krawPosn - krawPosm - otherPosn - otherPosm;

    long double ret = myKraw*2/existing;
    
    cout<<ret<<"\n";
    
    // debug(allPos);
    // debug(allKraw);
    // debug(krawPosn);
    // debug(krawPosm);
    // debug(otherPosn);
    // debug(otherPosm);
    // debug(existing);
    // debug(myKraw);

    return 0;
}




/*
    __builtin_popcount count total set bits on a given integer
    (use __builtin_popcountll for long long).

4 6
...C..
.B.C.B
C.CB.C
.B.C..
103
DDDDDDGDGPPLPDLDPGLDPGLDPGDLPGLGPDLGDPLGDPLGDPLGPDLGPDLGPDLGDGPLDPLGLDLGPDLGPDLPDLGPDLGPDLGPDLGPDLGPDLG

4 2 .C C. BC C. 3 GDL

4 4
.BBB
.BB.
.BC.
.CCB
6
LLDLDP

43 50
CBC...C.B.....C..BC.CBC...BCC.B.BB.B...B..CB.B...B
.....BB.C.B.C.CCB.....CCC..C.CC..B..BC...BBCCBB..C
.CB.......CB.C.B.BC.C..C.B..B.....B.C...CC.B.CB.B.
.BBB.BCCC..CBBCBC.....C..B.B.CCB......CB.BC.BCC..C 
.....B.C.C..B.BBBC.C.....BCBC...CB....C.CC.C..B.B. 
B.BBCCB....BC.B...B.C.BC...BBB..CB.B...C..BCCBB..C 
.CBB...BCC....CC.CB..C.CC.C.CCB.B...BC.BBB..BB.BBC
CBC..B.....BC.C..C...B.CBC..BCCC..BB.BBBB..BB...CC
C.B...BB.B..C...C.CBBBCCBB..C.BCB..C.CC...B...BC.B 
.C..C..BB..C.C...C.C..BC.CCB...........CC....CCCBB 
BC......B..B.B.C.C.B..B..B..BB.BC.BC.CC....CB.BC.B 
....BC......C.BBBB.CB..CC..B....B..C...CB..B...C.C
BB.B.C.C.C.C..B...C......BC....BBBCBB...BB...B.... 
B..CBB...B.CB..B.B.......BCCB.C......BCC.B...C..BB 
CBB.C.B......C...BB.CBCB.B.CBCBCCCB.B.CC.C.CBC.CB. 
..C..C.B.BBC...CC....C...B..BB..BCBCCC.BBCC..CB...
.C...CB.B..BC..B.B.CC..CBCB..C........C..CB...B..C 
..C.B.BCC.CCCC.CC......C.C.CC.CBCBC.....C.BC.CBC..
C...CB......CBCB...CBCB......C..C..C..CCB.BCC.BB..
CB.BBC..C..B...B.B...C.C..BBC..BB.BB..C..B.B..B..C
.B.C.....BBB.C.B.BC.BBCC...CC..B.C..C.C.BB.B...BBC
CC..CBCBBC.B...C..BC..BBC...CB.CBB.B........C...C. 
C..C..BCCBBCC...BB......C.CC..BB.B...B.B..CBBC.BCC
.C.BCBCCC.B.C..B.B.B...BBCCCCBBCB...B.B.C..CB....C
..C..B.C..CC.C..BC.BB.CCCB.C...C..C...B..B.....B.B 
.C.B..B.BCCB.B.CCC...CB.C.C.CCC..CBCBBCBBC.BB...B.
BC..BCC.CBBBCB.C....BBB.BC.CC.C...CC..CCCCBC..CC.. 
.CB.BB.C.B..C.C.B...B.B...C.C...CBBC.CBB..BB...CBC 
B..B.BCB....BBBCB....BB.C....CB..CC..B.C......B.C. 
BCB.B.B..C..C.C.B..CCB..CC..B.BC.CBC..BB.CCBBC....
.B......C..C......CB.BB..BBC..C.BBC.CB.B.B.C.BC.B.
CCC..CBB.CBCBB.BB.....CC.CB.BCBCB.CC.C.CB.B.BB.BB.
BC..BC.BCB..C..B..CB.BCC.CC......BCC.B..C.C..B.CBB
........BB..B......CBB..B.CBBCC.CC.BCCBCCBC.BC.BB. 
...C...CC..BCCCCBB.C......CCCBB.CBCC.BB.C..BC.C..C
..BBCB...B.BC....C..C....B....CC..BBB..C..BC.B..B.
.B.....BB.B...BBB.....B..BCC..B.BCB...CBC..B...B.B 
.CCC..B.C.BBB..C.BB...CBB.BCBBBBB...BB.CC..CB..C.C 
..B.C..BCB.C..BBC.CB..CBC..B.B.B....B.C..C.BCC.CCC 
CC...C..CBCBBBCC.C.CB...C...BCB.BC..C.CBC.BBBC.CB. 
B....CB.B..B..B.C..B.B...CC..C.B.C.BC...BC.C..BCCC 
...C.CCBC.B..C.B...BB..B.C.CBC.CB...C.B.....BB..C. 
CB.CBCC.CB.B....CBB.......CC....B....C.........BCC
3
DPG

180 
DLPPPGDGGL
LGGDD
PDGDGLLDLPGDDDD
PLLLPGDDLGGDGGP
DPPPLLPPPLDDDGDGPLDGGLLPLLPGGGDPGLLGDDLPDDLGL
PLGLGPGLLDDLDPGGPPDDPDGLPPDGPDGPLGLGPDGLDLPGL
PPDLDPDGPLDGDPLPPPGDGPDLGPLLPDLGDDGGLLLLLLDLD

*/