1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
#include<bits/stdc++.h>
 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("trapv")
 
#define st first
#define nd second
#define pb push_back
#define pp pop_back
#define eb emplace_back
#define mp(a, b) make_pair(a, b)
#define all(x) (x).begin(), (x).end()
#define rev(x) reverse(all(x))
#define sor(x) sort(all(x))
#define sz(x) (int)(x).size()
#define rsz(x) resize(x)
 
using namespace std;
 
///~~~~~~~~~~~~~~~~~~~~~~~~~~
 
template <typename H, typename T> 
ostream& operator<<(ostream& os, pair<H, T> m){
	return os <<"("<< m.st<<", "<<m.nd<<")";
}
template <typename H> 
ostream& operator<<(ostream& os, vector<H> V){
	os<<"{";
	for(int i=0; i<V.size(); i++){
		if(i)os<<" ";
		os<<V[i];
	}
	os<<"}";
	return os;
}
 
void debug(){cerr<<"\n";}
template <typename H, typename... T>
void debug(H h, T... t) {cerr<<h; if (sizeof...(t)) cerr << ", "; debug(t...);}
#define deb(x...) cerr<<#x<<" = ";debug(x);
 
///~~~~~~~~~~~~~~~~~~~~~~~~~
 
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii > vii;
typedef vector<ll> vl;
typedef vector<pll> vll;
typedef string str;
 
#define BOOST ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
 
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
 
const int N=2e5+5, INF=1e9+5, mod=1e9+7;
ll npok(int n, int k){
	__int128 ans=1;
	for(int i=n-k+1; i<=n; i++)ans*=i;
	for(int i=2; i<=k; i++)ans/=i;
	return ll(ans);
}
int main(){
	//BOOST;
	int n, m, k=0;
	cin>>n>>m;
	bool b=0;
	for(int i=0; i<n; i++){
		str s;
		cin>>s;
		for(int j=0; j<m; j++){
			if(s[j]=='O'){
				b^=(i^j)&1;
				k++;
			}
		}
	}
	bool b2=0;
	int deg=0;
	vector<str> s(n);
	for(int i=0; i<n; i++){
		cin>>s[i];
	}
	for(int i=0; i<n; i++){
		for(int j=0; j<m; j++){
			if(s[i][j]=='O'){
				b2^=(i^j)&1;
				if(i+1<n && s[i+1][j]!='O')deg++;
				if(i-1>=0 && s[i-1][j]!='O')deg++;
				if(j+1<m && s[i][j+1]!='O')deg++;
				if(j-1>=0 && s[i][j-1]!='O')deg++;
			}
		}
	}
	if(b!=b2){
		cout<<0;
		return 0;
	}
	__int128 sum=npok(n*m-2, k-1);
	sum*=n*(m-1)+m*(n-1);
	__float128 ans=deg;
	ans/=sum;
	cout<<fixed<<setprecision(15)<<ld(ans);
}