#include <bits/stdc++.h>   using namespace std;   int n, m, x, y;   int b[1005], a[1005];   int F1[1005], F2[1005];   int main() {     char ch;     cin >> n >> m >> x >> y;     for (int i = 1; i <= n; ++i)       for (int j = 1; j <= m; ++j) {         cin >> ch;         if (ch ==  # ) b[j]++;       }     for (int i = 1; i <= m; ++i) a[i] = a[i - 1] + b[i];     for (int i = 1; i <= m; ++i) {       F1[i] = 10000000;       F2[i] = 10000000;     }     for (int i = x; i <= y; ++i) {       F1[i] = a[i];       F2[i] = n * i - a[i];     }     for (int i = x + 1; i <= m; ++i) {       for (int j = x; j <= y; ++j)         if (i - j >= x) {           if (F1[i] > F2[i - j] + a[i] - a[i - j])             F1[i] = F2[i - j] + a[i] - a[i - j];           if (F2[i] > F1[i - j] + n * j - a[i] + a[i - j])             F2[i] = F1[i - j] + n * j - a[i] + a[i - j];         }     }     if (F1[m] > F2[m])       cout << F2[m];     else       cout << F1[m];     return 0;   }   