int main() {
	double a;
	scanf("%lf\n",&a);
	char jjla[501];
	char jjlb[501];
	int i,j;
	gets(jjla);
	gets(jjlb);
	int b,c;
	b=strlen(jjla);
	c=strlen(jjlb);
	if(b!=c){
		printf("error");
	}else{
		int cwzm;
		cwzm=0;
		for(j=0;j<b;j++){
			if(jjla[j]!='A'&&jjla[j]!='G'&&jjla[j]!='T'&&jjla[j]!='C'){
					cwzm++;
			}
		}
		for(j=0;j<b;j++){
			if(jjlb[j]!='A'&&jjlb[j]!='G'&&jjlb[j]!='T'&&jjlb[j]!='C'){
					cwzm++;
			}
		}
		if(cwzm==0){
			int xt;
			xt=0;
			for(i=0;i<b;i++){
				if(jjla[i]==jjlb[i]){
					xt++;
				}
			}
			double bl;
			bl=(double)xt/b;
			if(bl>a){
				printf("yes");
			}else{
				printf("no");
			}
		}else{
			printf("error");
		}
	}
	return 0;
}

