function main(input) {
  var x = input[0].split(" ")[0]-0;
  var a = input[0].split(" ")[1]-0;
  var b = input[0].split(" ")[2]-0;
  console.log(Math.abs(x-a)>Math.abs(x-b)?"B":"A");
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"))
