#include <bits/stdc++.h> using namespace std; int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int H,W; cin >> H >> W; vector<string> S(H),T(H); for(auto &s : S) cin >> s; for(auto &t : T) cin >> t; for(auto &s : S) for(auto &c : s) c ^= '.'^'#'; vector<string> S2(H,string(W,'.')); for(int i=0; i<H; i++) for(int k=0; k<W; k++) S2.at(H-1-i).at(W-1-k) = S.at(i).at(k); if(S != T){ swap(S,S2); if(S == T){ double answer = 0,all = 1; for(int i=1; i<=100; i+=2){ double now = 1.0-pow(0.5,i); answer += all*now*(i+1); all -= all*now; } cout << fixed << setprecision(20) << answer << endl; } else cout << "-1" << endl; } else if(S2 != T) cout << fixed << setprecision(20) << 3.5317401904617327 << endl; else{ double answer = 0,all = 1; for(int i=0; i<=100; i++){ double now = 1.0-pow(0.5,i); answer += all*now*(i+1); all -= all*now; } cout << fixed << setprecision(20) << answer << endl; } }