#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int cnt = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == '-')
      cnt--;
    else if (s[i] == '+')
      cnt++;
    if (cnt < 0) cnt = 0;
  }
  cout << cnt << endl;
}
