//: Playground - noun: a place where people can play


import Foundation
/*
func readInt(str : String) -> Int{
    return Int(str)  ?? 0
}

func splitInt(str : String,array :inout [Int]) ->(){
    var temp : String = ""
    for itr in str{
        if itr == " "{
            array.append(Int(temp) ?? 0)
            print(temp)
            temp =  ""
        } else {
            temp += String(itr)
        }
    }
    array.append(Int(temp) ?? 0)
}
*/
/*
 
 
 
 
 let string = "abc"  // "abc"(String型)
 let characters = string.characters  // String.CharacterView型
 
 // 2文字目を取得
 let bIndex = characters.index(characters.startIndex, offsetBy: 1)
 let b = string[bIndex]  // "b"
 
 // 最後の文字を取得
 let cIndex = characters.index(characters.endIndex, offsetBy: -1)
 let c = string[cIndex]  // "c"
 
 */

var str: String = readLine() ?? ""
var array :[Int] = []
var temp:String = ""
let char = str.characters
for i in 0...str.characters.count{
    let index =  char.index(char.startIndex,offsetBy: i)
    
    if str[index] == " "{
        array.append(Int(temp) ?? 0);
        temp = "";
    } else {
        temp += String(str[index]);
    }
}
if  abs(array[0]-array[1]) > abs(array[0]-array[2]){
    print("a")
}else{
    print("b")
}


