#include<cstdio>
#include<cstring>
using namespace std;
double q;
int z,e;
char a[505],b[505];
int main ()
{
	scanf("%lf%s%s",&q,a+1,b+1);
	z=strlen(a+1);
	for(int i=0;i!=z;i++){
		if(a[i]==b[i]) e++;
	}
	if((1.0*(double)e/z)>q) printf("yes");
	else printf("no");
	return 0;
	
}