#include<stdio.h>

int main(void){

char s[4];

scanf("%s",&s);

if(s[0]=='A'&&s[1]=='B'&&s[2]=='C'&&s[3]=='\0'){printf("ARC");}
else if(s[0]=='A'&&s[1]=='R'&&s[2]=='C'&&s[3]=='\0'){printf("ABC");}

return 0;
}
