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 10.0.0) (judge verdict: Accepted)

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <cmath>
#include <iomanip>
#include <set>
using namespace std;
typedef long long ll;

int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;

  int ans = 0;
  int current = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'I') {
      current++;
    } else {
      current--;
    }

    ans = max(ans, current);
  }
  cout << ans << endl;
  return 0;
}