int main(){
	char mid,a[100],b[100];
	int i,j,stop,lengtha,lengthb,dif,error;
	double r,odd;
	dif=0;
	error=0;
	scanf("%lf",&odd);
	getchar();
	gets(a);
	gets(b);
	lengtha=strlen(a);
	lengthb=strlen(b);
	for(i=0;i<lengtha;i++){
		if(a[i]==b[i]){
			dif++;
		}
		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')){
			error++;
		}
	}
	r=1.0*dif/lengtha;
//	printf("error=%d\n",error);
	if(error>0||lengtha!=lengthb){
		printf("error");
	}else{
		if(r>odd){
			printf("yes");
		}else{
			printf("no");
		}
	}
	scanf("%d",&stop);
	return 0;
}