#include<bits/stdc++.h> 
using namespace std; 
const int N=1e3+10; 
int main(){ 
    char a[N],b[N]; 
    double n; 
    cin>>n>>a>>b; 
    double cnt; 
    for(int i=0;i<strlen(a);i++) if(a[i]==b[i]) cnt++;  
    double r=cnt/strlen(a); 
    if(r>n) cout<<"yes";
    else cout<<"no"; 
}