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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include<stdio.h>

int main(){

	int N,sum,max = 0;
	scanf("%d",&N);

	char S[N];
	scanf("%s",S);

	for(int i=0; i<N; i++){
		if(S[i]=='I'){
			sum ++;
		}else{
			if( sum == 0 ){
				/*何もしない*/
			}else{
				sum --;
			}
		}
		if( max < sum ){
			max = sum;
		}

	}
	printf("%d",max);

	return 0;


}