function Main(input) {
  const inputs = input.split(" ");
  const x = parseInt(inputs[0], 10);
  const a = parseInt(inputs[1], 10);
  const b = parseInt(inputs[2], 10);
  
  const distA = Math.abs(x - a);
  const distB = Math.abs(x - b);
  if (distA < distB) {
    console.log('A');
  } else {
    console.log('B');
  }
}

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