import Foundation

let Nstr = readLine()!
var N = Int(Nstr)!
var result = ""

func getAlpha(_ num: Int) -> String {
    switch num {
    case 0:
        return "z"
    case 1:
        return "a"
    case 2:
        return "b"
    case 3:
        return "c"
    case 4:
        return "d"
    case 5:
        return "e"
    case 6:
        return "f"
    case 7:
        return "g"
    case 8:
        return "h"
    case 9:
        return "i"
    case 10:
        return "j"
    case 11:
        return "k"
    case 12:
        return "l"
    case 13:
        return "m"
    case 14:
        return "n"
    case 15:
        return "o"
    case 16:
        return "p"
    case 17:
        return "q"
    case 18:
        return "r"
    case 19:
        return "s"
    case 20:
        return "t"
    case 21:
        return "u"
    case 22:
        return "v"
    case 23:
        return "w"
    case 24:
        return "x"
    case 25:
        return "y"
    
    default:
        fatalError()
    }
}



func solution() {
    var isDev = 0
    
    if N == 26 {
        print("z")
        return
    }
    
    while N > 26 {
        isDev = N % 26
        result = getAlpha(N % 26) + result
        N /= 26
    }
    
    if N == 26 {
         result = "z" + result
         print(result)
         return
     }
     
     if isDev == 0 {
         result = getAlpha(N - 1) + result
     } else {
         result = getAlpha(N) + result
     }

     print(result)
}


solution()