ABC052B - Increment Decrement

問題：B - Increment Decrement

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

#define REP(i, n) for (int i = 0; i < (n); ++i)

int main(void) {
    int n, x = 0, max_x = 0;
    string s;

    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    cin >> s;
    REP(i, n) {
        x += (s[i] == 'I')? 1 : -1;
        max_x = max(max_x, x);
    }

    cout << (max_x < 0? 0 : max_x) << "\n";
    return 0;
}