int main()
{
	char w1[256],w2[256];
	int n,m,i,j=0,A=1;
	double a,c;
	scanf("%lf%s%s",&a,&w1,&w2);
	n=strlen(w1);
	m=strlen(w2);
	if(n!=m)printf("error");
    if(n==m){
		for(i=0;i<n;i++){
			if((w1[i]=='A'&&w2[i]=='A')||(w1[i]=='G'&&w2[i]=='G')||(w2[i]=='T'&&w1[i]=='T')||(w2[i]=='C'&&w1[i]=='C'))
				j++;
		    if((w1[i]!='A'&&w1[i]!='T'&&w1[i]!='G'&&w1[i]!='C')||(w2[i]!='A'&&w2[i]!='T'&&w2[i]!='G'&&w2[i]!='C'))
			{	A=0;
			}
		}
		c=(double)j/n;
	if(A==0) printf("error");
	else if(A==1&&c>a) printf("yes");
	else if(A==1&&c<=a) printf("no");
	}
	return 0;
}