#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, c = 0, d = 0, k;
  string str;
  cin >> n >> str;
  for (int i = 0; i < n; i++) {
    if (str[i] == '-') c++;
  }
  if (c == n) {
    cout << 0 << endl;
    return 0;
  } else if (str[0] == '-') {
    for (int i = 0; i < n; i++) {
      if (str[i] == '-') {
        continue;
      } else {
        k = i;
        break;
      }
    }
    for (int i = k; i < n; i++) {
      if (str[i] == '+')
        d += 1;
      else {
        d -= 1;
        if (d < 0) d = 0;
      }
    }
  } else {
    for (int i = 0; i < n; i++) {
      if (str[i] == '+')
        d += 1;
      else {
        d -= 1;
        if (d < 0) d = 0;
      }
    }
  }
  cout << d << endl;
  return 0;
}
