文件目录

#include <iostream>
using namespace std;
int main()
{
    int k;
    string s;
    cin >> k >> s;
    char c = s[0];
    int t = 1;
    if (k == t)
    {
        cout << c;
        return 0;
    }
    for (int i = 1; s[i]; i++)
    {
        if (s[i] == c)
        {
            t++;
            if (k == t)
            {
                cout << c;
                return 0;
            }
        }
        else
        {
            c = s[i];
            t = 1;
        }
    }
    cout << "No";
    return 0;
}