PAT--Raffle for Weibo Followers

#include <iostream>
#include <map>

using namespace std;

int main() {
    int m, n, s;
    scanf("%d%d%d", &m, &n, &s);
    
    string str;
    map<string, int> mapp;
    
    bool flag = false;
    for (int i = 1; i <= m; i++) 
    {
        cin >> str;
        if (mapp[str] == 1) 
            s = s + 1;
        if (i == s && mapp[str] == 0) 
        {
            mapp[str] = 1;
            cout << str << endl;
            flag = true;
            s = s + n;
        }
    }
    if (flag == false) 
        cout << "Keep going..." << endl;
    return 0;
}