"use strict";

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