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)

// ABC052 B - Increment Decrement
#include <stdio.h>

int main(void) {
    int N;
    char S[101];
    // input
    scanf("%d", &N);
    int i = 0;
    for(i = 0; i < N; i++) {
        scanf("%c", &S[i]);
    }
    S[i] = '\0';

    int x = 0;
    int result = 0;
    i = 0;
    while(S[i] != '\0') {
        if (S[i] == 'I') {
            x++;
        } else if(S[i] == 'D') {
            x--;
        }
        if (x > result) {
            result = x;
        }
        i++;
    }

    printf("%d\n", result);
}