#include <iostream>
using namespace std;
int main(){
    double k=0.0;
    cin>>k;
    double cnt=0.0;
    string a,b;
    cin>>a>>b;
    for(int i=0;i<a.size();i++){
        if(a[i]==b[i])cnt++;
    }
    double len=a.size();
    if(cnt/len>=k)cout<<"yes";
    else cout<<"no";
return 0;
}