int main(){
	int i,z=0,len1,len2;
	double n;
    char a[500],b[500];
	scanf("%lf%s%s",&n,a,b);
	
	len1=strlen(a);
	len2=strlen(b);
	if(len1!=len2)
		printf("error");
	else{
	for(i=0;i<len1;i++){
		if((a[i]!='A'&&a[i]!='T'&&a[i]!='G'&&a[i]!='C')||(b[i]!='A'
			&&b[i]!='T'&&b[i]!='G'&&b[i]!='C')){
			printf("error");
			z=-1;
			break;
		}
		else{
		if(a[i]==b[i])
		z+=1;
		}
	}
	if(z>=0){
	   if((1.0*z/len1)>n)
		printf("yes");
	    else
		printf("no");
	
	}
	}




	return 0;
}