int main()
{
	char s1[505],s2[505];
	double n,m=0,len1,len2,flag=0;
	int i;
	scanf("%lf",&n);
	scanf("%s",s1);
	scanf("%s",s2);
	len1=strlen(s1);
	len2=strlen(s2);
	for(i=0;i<len1;i++)
	{
		if((s1[i]=='A')||(s1[i]=='T')||(s1[i]=='C')||(s1[i]=='G'))
			continue;
		else
		{
			flag=1;
			break;
		}
	}
	for(i=0;i<len2;i++)
	{
		if((s2[i]=='A')||(s2[i]=='T')||(s2[i]=='C')||(s2[i]=='G'))
			continue;
		else
		{
			flag=1;
			break;
		}
	}

	if((len1!=len2)||(flag==1))
	{
		printf("error");
	}
	else
	{
	for(i=0;i<=len1;i++)
	{
		if(s1[i]==s2[i])
		{
			m++;
		}
	}
	m=m/len1;
	if(m>n)
		printf("yes");
	else
		printf("no");
	}


	return 0;
}