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: Accepted)

// Author: Vamsi Krishna Reddy Satti
// With love for Competitive Programming!
 
#include <bits/stdc++.h>
using namespace std;
 
#define fast_io ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
#define cout_precision cout.setf(ios::fixed); cout.precision(32);
 
using ll = int64_t; using vll = vector<ll>; using vvll = vector<vll>;
using pll = pair<ll, ll>; using vpll = vector<pll>; using vvpll = vector<vpll>;
using ld = long double;
 
// ------------------------------------------------------------------------------------------------

ll n, ans;
string s;

int main() {
    fast_io; cout_precision;
    cin >> n >> s;
    ans = 0;
    for (ll i = 0, x = 0; i < n; i++) {
        if (s[i] == 'I') {
            x++;
        } else {
            x--;
        }
        ans = max(ans, x);
    }
    cout << ans << endl;
}