int main()
{
	double m,n;
	int len1,len2,count=0,i;
	char s1[100],s2[100];
	scanf("%lf",&m);
	scanf("%s",s1);
	scanf("%s",s2);
	len1=strlen(s1);
	len2=strlen(s2);
	if(len1==len2)
	{
		for(i=0;i<len1;i++)
		{
		    if(s1[i]!='A'&&s1[i]!='T'&&s1[i]!='C'&&s1[i]!='G'||s2[i]!='A'&&s2[i]!='T'&&s2[i]!='C'&&s2[i]!='G')
			{    
				count=len1+1;
			    break;
			}
			if(s1[i]==s2[i])
				count++;
		}
		n=1.0*count/len1;
		if(count>=len1+1)
			printf("error\n");
		if(n>m&&n<=1)
			printf("yes\n");
		else if(n<=m)
			printf("no\n");
	}
	else
		printf("error\n");
	return 0;
	
}
