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