#include <bits/stdc++.h>
int main(void) {
  int n, sum = 0;
  scanf("%d", &n);
  getchar();
  char str[n];
  gets(str);
  for (int i = 0; i < n; i++) {
    if (str[i] == '+')
      sum++;
    else if (str[i] == '-' && sum != 0)
      sum--;
  }
  printf("%d\n", sum);
  return 0;
}
