#include<iostream> #include<cstdio> #include<cstring> using namespace std; int main(){ char s[2500]; int k,len,sum=1,i; cin>>k; cin>>s; len=strlen(s); for(i=0;i<len;i++){ if(sum==k){ cout<<s[i]<<endl; return 0; } if(s[i]==s[i+1]) sum++; else sum=1; } cout<<"No"<<endl; return 0; }