#include<iostream>
#include<string>
using namespace std;
int i;
double t,cou,ans;
string s1,s2;
int main()
{
    //freopen("input1","r",stdin);
    //freopen("output1","w",stdout);
    cin>>t>>s1>>s2; 
    for(i=0;i<s2.length();i++) 
        if(s1[i] == s2[i])
            cou=cou+1;
    ans=cou/s1.length();
    if(ans >= t) cout<<"yes"<<endl;
    else cout<<"no"<<endl;
    return 0;
}