import Foundation
//10^15
//1000000000000001
// Decimal型の有効桁数は38桁
var N = UInt(readLine()!)!
let m = UInt(26)

var a: UInt
var output = ""
var c: String

repeat {
    a = N % m
    N = N / m

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

print(output)
