function main(input) {
  input = input.trim();
  const [x,a,b] = input.split(" ").map(Number);

  if(Math.abs(x - a) < Math.abs(x - b)){
    console.log("A");
  }else{
    console.log("B");
  }
    
}
main(require("fs").readFileSync("/dev/stdin", "utf8"));