function Main(input){
  input=input.split("\n");
  input=input[0].split(" ");
  const x = parseInt(input[0],10);
  const a = parseInt(input[1],10);
  const b = parseInt(input[2],10);
  var dist_xa = Math.abs(x-a);
  var dist_xb = Math.abs(x-b);

  console.log(dist_xa<=dist_xb ? "A" : "B");
}

Main(require("fs").readFileSync("/dev/stdin","utf8"));
