int main(){
	int i,n,l1,l2,k;
	n=0;
	k=1;
	double s;
	char x1[501],x2[501];
	scanf("%lf",&s);
	scanf("%s",x1);
	scanf("%s",x2);
	l1=strlen(x1);
	l2=strlen(x2);
	if(l1!=l2){
		printf("error");
	}else{
		for(i=0;i<l1;i++){
			if(!(x1[i]=='A'||x1[i]=='C'||x1[i]=='G'||x1[i]=='T')){
				printf("error");
				k=0;
				break;
			}
			if(!(x2[i]=='A'||x2[i]=='C'||x2[i]=='G'||x2[i]=='T')){
				printf("error");
				k=0;
				break;
			}
			if(x1[i]==x2[i]){
				n++;
			}
		}
		if(k){
		    if(1.0*n/l1>s){
			    printf("yes");
			}else{
			    printf("no");
			}
		}
	}
	return 0;
}