#include<iostream>
#include<string>
using namespace std;
int main(){
    double x=0;
    double k;
    string s1,s2;
    cin>>k>>s1>>s2;
    for(int i=0;i<s1.size();i++){
        if(s1[i]==s2[i]) x++;
    }
    if(x/s1.size()>=k) cout<<"yes";
    else cout<<"no";
    return 0;
}