#include<bits/stdc++.h>
using namespace std;
int main(){
double k;
cin>>k;
string a,b;cin>>a>>b;
int cnt=0;
int n=a.length();
for(int i=0;i<n;i++){
if(a[i]==b[i]){
cnt++;
}
}
double p=(double)cnt/n;
if(p>=k){
cout<<"yes";
}
else{
cout<<"no";
}
return 0;
}
