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

}