#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
const int N = 2000086, MOD = 998244353, INF = 0x3f3f3f3f;
ll res;
int n, m, cnt, w[N];


char s[N];
int main() {
    cin >> n;
    scanf("%s", s + 1);
    int c0 = 0, c1 = 0, c2 = 0;
    for (int i = 1; i < n + 1; i++) {
        if (s[i] == '+') {
            c2 = max({ c0, c1, c2 }) + 1;
        } else if (s[i] == '0') {
            c1 = c0 + 1;
        } else {
            c0++;
        }
    }
    printf("%d\n", max({ c0, c1, c2}));
    return 0;
}