Problem:
Score : 200 points

Problem Statement

You have an integer variable x.
Initially, x=0.

Some person gave you a string S of length N, and using the string you performed the following operation N times.
In the i-th operation, you incremented the value of x by 1 if S_i=I, and decremented the value of x by 1 if S_i=D.

Find the maximum value taken by x during the operations (including before the first operation, and after the last operation).

Constraints

1≤N≤100

|S|=N

No characters except I and D occur in S.

Input

The input is given from Standard Input in the following format:

N
S

Output

Print the maximum value taken by x during the operations.

Sample Input 1

5
IIDID

Sample Output 1

2

After each operation, the value of x becomes 1, 2, 1, 2 and 1, respectively. Thus, the output should be 2, the maximum value.

Sample Input 2

7
DDIDDII

Sample Output 2

0

The initial value x=0 is the maximum value taken by x, thus the output should be 0.

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#define max(a, b) ((a)<(b) ? (b) : (a))
int main(){
  long long int x = 0, ans = 0;
  int n;  scanf("%d", &n);
  char s[102];  scanf("%s", s);

  for(int i=0; i<n; i++){
    if(s[i] == 'D'){
      x--;
    }else{
      x++;
      ans = max(ans, x);
    }
  }
  printf("%lld\n", ans);
  return 0;
}