#include<bits/stdc++.h>
using namespace std;
int main() {
	freopen("copy.in","r",stdin);
	freopen("copy.out","w",stdout);
    int n, m;
    cin >> n >> m;
    int grid[n][m];
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> grid[i][j];
        }
    }
    int dp[n][m];
// 初始化第一行和第一列的dp值
for (int i = 0; i < n; i++) {
    if (grid[i][0] == ')') {
        dp[i][0] = dp[i-1][0] + 1;
    }
}                              
for (int j = 0; j < m; j++) {
    if (grid[0][j] == ')') {
        dp[0][j] = dp[0][j-1] + 1;
    }
}
for (int i = 0; i < n; i++) {
    for (int j = 0;j < m; j++) {
        if (grid[i][j] == '(') {
            dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
        } else {
            dp[i][j] = max(dp[i-1][j], dp[i][j-1]) + 1;
        }
    }
}
cout << dp[n-1][m-1] << endl;
return 0;
}