const Main = (input)=>{
	var xs = input.trim().split(' ').map(v=>parseInt(v,10));
    var a = Math.abs(xs[0] - xs[1]);
    var b = Math.abs(xs[0] - xs[2]);
    if(a > b){
    console.log('B');
    }else if(a < b){
    console.log('A');
    }
}
Main(require("fs").readFileSync("/dev/stdin","utf8"));