function main (s) {
	s=s.split(" ");
	for(var i=0;i<3;i++)s[i]=parseInt(s[i]);
    console.log((Math.abs(s[0]-s[1])<Math.abs(s[0]-s[2]))?"A":"B");
}
 
main(require('fs').readFileSync('/dev/stdin', 'utf8'));