function main(input){
    var tmp = input.split(" ");
    var x = Number(tmp[0]);
    var a = Number(tmp[1]);
    var b = Number(tmp[2]);

    if(Math.abs(x-a) < Math.abs(x-b))
        console.log("A");
    else
        console.log("B");
}

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