#include #include #include using namespace std;

int main() { int n, m, s, t; cin >> n >> m >> s >> t;

vector<vector<int>> a(n + 1, vector<int>(m + 1, 0));
for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
        cin >> a[i][j];
    }
}

// 二维前缀和
vector<vector<int>> sum(n + 1, vector<int>(m + 1, 0));
for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
        sum[i][j] = a[i][j] + sum[i-1][j] + sum[i][j-1] - sum[i-1][j-1];
    }
}

int minSum = INT_MAX;

// 枚举所有 s*t 子矩阵的左上角
for (int i = 1; i + s - 1 <= n; i++) {
    for (int j = 1; j + t - 1 <= m; j++) {
        int x2 = i + s - 1;
        int y2 = j + t - 1;
        int subSum = sum[x2][y2] - sum[i-1][y2] - sum[x2][j-1] + sum[i-1][j-1];
        if (subSum < minSum) {
            minSum = subSum;
        }
    }
}

cout << minSum << endl;

return 0;

}