function GetDistance(between){
  if (between < 0){
  	between = between*-1;
    return between
  }
  return between
}

function main(input) {

  	var BasePoint = input[0];
  	var Apoint = input[1];
  	var Bpoint = input[2];
  
  	AbetweenBase = Apoint - BasePoint;
  	AbetweenBase = GetDistance(AbetweenBase);
  
  	BbetweenBase = Bpoint - BasePoint;
  	BbetweenBase = GetDistance(BbetweenBase);
  
  	if (AbetweenBase > BbetweenBase){
     	console.log("B"); 
    } else if(BbetweenBase > AbetweenBase){
      	console.log("A");
    } else{
      console.log("error");
    }
  	
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));