#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int solve(int N, const string& S) {
    int prefix_sum = 0;
    int min_prefix_sum = 0;
    int max_difference = 0;
    
    for (char c : S) {
        prefix_sum += (c == '0') ? 1 : -1;
        max_difference = max(max_difference, prefix_sum - min_prefix_sum);
        min_prefix_sum = min(min_prefix_sum, prefix_sum);
    }
    
    return max_difference;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    int N;
    string S;
    cin >> N >> S;
    
    cout << solve(N, S) << endl;
    
    return 0;
}