process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = []
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});

reader.on('line', (line) => {
  lines.push(line);
});

reader.on('close', () => {
 var mae = lines[0];
 if(mae = "ARC"){
   console.log("ABC");
 }else if(mae = "ABC"){
   console.log("ARC");
 }
});