#include <bits/stdc++.h>
using namespace std;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int N;
    string S;
    cin >> N >> S;
    int D[3]{};
    for (char c : S)
    {
        if (c == '-')
            D[0] = D[0] + 1;
        else if (c == '0')
            D[1] = max(D[0] + 1, D[1]);
        else
            D[2] = max({D[0], D[1], D[2]}) + 1;
    }
    cout << max({D[0], D[1], D[2]}) << endl;
}