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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    string s;
    cin >> n >> s;
    vector<int> a(n);
    int cur = 2;
    for(int i = 0; i < n; i++){
        if(s[i] == '+') a[i] = cur++;
    }
    cur = -2;
    for(int i = n - 1; i >= 0; i--){
        if(s[i] == '-') a[i] = cur--;
    }
    vector<int> b;
    for(int i = 0; i < n; i++){
        int p = lower_bound(b.begin(), b.end(), a[i]) - b.begin();
        if(p == b.size()) b.emplace_back(a[i]);
        else b[p] = a[i];
    }
    cout << b.size() << '\n';
}