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)

#include <bits/stdc++.h>

using namespace std;
#define sf(n) scanf("%d", &n)
#define pd(n) printf("%.12lf", n)
#define pf(n) printf("%d", n)
#define p() printf("\n")
#define ps() printf(" ")
#define ll long long
#define ull unsigned long long
#define MAX 1e9
#define mod 1000 * 1000 * 1000 + 7
#define ex 1e18
#define dbl 2e09
#define qu(q) queue<int> q
#define pqu(q) priority_queue<int> q
#define len(s) s.length()
#define sz(x) int(x.size())
#define pb(x) push_back(x)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define F first
#define S second
#define clr(x) x.clear()
#define LOG(x) std::cout << x << std::endl;

const int INF = 0x3f3f3f3f;
const ll LL_INF = 0x3f3f3f3f3f3f3f3f;
const double PI = 3.14159265359;

int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};

int main()
{
    int n;
    cin>>n;
    string s;
    cin>>s;
    int ans=0,cnt=0;;
    for(int i=0;i<n;++i){
        if(s[i]=='I'){
            cnt+=1;
            ans=max(cnt,ans);
        }
        else
        {
            cnt-=1;
        }
        
    }
    cout<<ans<<endl;
    return 0;
}