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