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 <algorithm>
#include <iostream>
#include <vector>
#include <string>
#include <climits> // FOO_MAX, FOO_MIN
#include <cmath> 
#include <cstdlib> // abs(int)
#include <numeric>
#include <iomanip>
#include <map>
#include <set>

using namespace std;

#define roundup(n,d) ( ((n) + ((d)-1)) / (d) )
#define assign_max(into, compared) (into = max((into), (compared)))
#define assign_min(into, compared) (into = min((into), (compared)))
#define rep(i,n) for(long long i = 0;i < n;++i)
#define v_in(v) for(auto&& i : v) cin >> i
#define FAST_IO ios::sync_with_stdio(false); cin.tie(nullptr);
#define fix(n) fixed << setprecision(n)
#define ALL(v) v.begin(),v.end()

#define PI 3.14159265358979323846

using ll = long long;
using ull = unsigned long long;
using vll = vector<long long>;
using vvll = vector<vector<long long>>;


int main(void){
    FAST_IO
    
    string s;
    ll n;
    cin >> n >> s;
    ll x = 0;
    ll max_x = 0;
    rep(i,n){
        if(s[i] == 'I'){
            x++;
        } else {
            x--;
        }
        assign_max(max_x,x);
    }
    cout << max_x << endl;
    return 0;
}