#include <bits/stdc++.h> using namespace std; int main() { int k; //至少出现了k次 cin >> k; string s; cin >> s; char c = s[0]; int cnt = 0; for(int i = 0; i < s.size(); ++i) { if(s[i] == c) { cnt++; } else { //cout << cnt << endl; if(cnt >= k) { cout << c << endl; return 0; } else { c = s[i]; cnt = 1; } } } if(cnt >= k) { cout << c << endl; return 0; } cout << "No" << endl; return 0; }