function Main(input){
	var tmp = input.split(" ");
	var a = Math.abs(tmp[0] - tmp[1]);
	var b = Math.abs(tmp[0] - tmp[2]);
	if(a < b){
           console.log("A");
         }else{
           console.log("B");
         }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));