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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <string>
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;

int main(){
	vector<int> sum_list;
	int n;
	int prevnum=0;
	string str;
	cin >> n >> str;
	for(auto i=str.begin(); i != str.end(); i++){
		if(*i == 'I'){
			prevnum++;
			sum_list.push_back(prevnum);
		} else {
			prevnum--;
		}
	}
	int max = *max_element(str.begin(), str.end());
	cout << max << endl;
}