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
#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(1);
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
//ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=10;
int n,m,par1,par2,c[20],k;
char s[N][N],t[N][N];
int main() {
	scanf("%d%d",&n,&m);
	for (int i=0;i<n;i++) {
		scanf("%s",s[i]);
		for (int j=0;j<m;j++) {
			if (s[i][j]=='O') par1^=(i+j)%2,++k;
			c[(i+j)%2]+=1;
		}
	}
	for (int i=0;i<n;i++) {
		scanf("%s",t[i]);
		for (int j=0;j<m;j++) {
			if (t[i][j]=='O') par2^=(i+j)%2;
		}
	}
	int eg=0;
	for (int i=0;i<n;i++) for (int j=0;j<m;j++) {
		if (i+1<n&&(t[i][j]=='O')!=(t[i+1][j]=='O')) ++eg;
		if (j+1<m&&(t[i][j]=='O')!=(t[i][j+1]=='O')) ++eg;
	}
	//fprintf(stderr,"%d\n",eg);
	if (par1!=par2) {
		puts("0");
		return 0;
	}
	int tote=(n-1)*m+n*(m-1);
	long double ans=0;
	auto binom=[&](int x,int y) {
		if (y<0||y>x) return (long double)0;
		long double ans=1;
		for (int i=1;i<=y;i++) ans=ans*(x+1-i)/i;
		return ans;
	};
	for (int p=0;p<=1;p++) {
		for (int c0=0;c0<=k-1;c0++) if ((k-1-c0+p)%2==par1) {
			ans+=binom(c[0]-1,c0)*binom(c[1]-1,k-1-c0);
		}
	}
	//printf("%.10Lf\n",ans);
	cout<<fixed<<setprecision(16)<<eg/(ans*tote)<<endl;
}