#include "bits/stdc++.h"
using namespace std;
#define int long long
signed main() {
int n, m;
cin >> n >> m;
vector <vector <int>> g(n * m + 2 * m);
for (int i = 0; i <= n; i ++) {
for (int j = 1; j <= m; j ++) {
char c;
cin >> c;
if (c == '0') {
// cout << (i - 1) * m + j << ' ' << i * m + j << endl;
g[max(0ll, (i - 1) * m + j - 1)].push_back(max(0ll, i * m + j - 1));
g[max(0ll, i * m + j - 1)].push_back(max(0ll, (i - 1) * m + j - 1));
}
}
}
for (int i = 1; i <= n; i ++) {
for (int j = 0; j <= m; j ++) {
char c;
cin >> c;
if (c == '0') {
// cout << (i - 1) * m + j << ' ' << (i - 1) * m + j + 1 << endl;
g[max(0ll, (i - 1) * m + j - 1)].push_back((i - 1) * m + j);
g[(i - 1) * m + j].push_back(max(0ll, (i - 1) * m + j - 1));
}
}
}
vector <int> comp, vis((n + 1) * (m + 1)), c;
auto dfs = [&](auto&& dfs, int i, int j) -> void {
if (i == 0 || j == 0 || i > n || j > m) return;
if (vis[(i - 1) * m + j - 1]) return;
vis[(i - 1) * m + j - 1] = 1; int k = (i - 1) * m + j - 1;
c.push_back(k);
for (int x : g[k]) {
int i1 = x / m + 1, j1 = x % m;
// cout << x << endl;
// cout << i1 << ' ' << j1 << endl;
dfs(dfs, i1, j1);
}
};
for (int i = 1; i <= n; i ++) {
for (int j = 1; j <= m; j ++) {
if (vis[(i - 1) * m + j - 1]) continue;
dfs(dfs, i, j);
if ((int)c.size() == 1) {
c.clear();
continue;
}
// cout << c.size() << endl;
comp = c;
// cout << i << ' ' << j << endl;
break;
}
if (comp.size()) break;
}
cout << -(int)comp.size() << endl;
return 0;
}
