int main(){
   int i,j=0,count1=0,count=0;
   char lian1[501],lian2[501];
   double bi,xiang;
   scanf("%lf",&bi);
   scanf("%s",lian1);
   scanf("%s",lian2);
   for(i=0;lian1[i]!='\0';i++){
	   count++;
   }
   for(i=0;lian1[i]!='\0';i++){
   if(lian2[i]==lian1[i])
   count1++;
   if(lian1[i]!='A'&&lian1[i]!='T'&&lian1[i]!='C'&&lian1[i]!='G'){
	   j=1;break;
   }
   if(lian2[i]!='A'&&lian2[i]!='T'&&lian2[i]!='C'&&lian2[i]!='G'){
	   j=1;break;
   }
   }
  
   if(j==1)
	   printf("error");
   if(j==0){
   xiang=count1*1.0/count;
 
   if(xiang>bi)
	   printf("yes");
   if(xiang<=bi)
	   printf("no");
   }
   
   return 0;
}