import Foundation

var n = Int(readLine()!)! - 1
var c = [Int]()

c += [n % 26 + 1]
n /= 26

guard n > 0 else {
    print(String(c.reversed().map{ Character(UnicodeScalar($0 + 96)!) }))
    exit(0)
}

while n >= 26 {
    c += [n % 26]
    n /= 26
}

c += [n % 26]

print(String(c.reversed().map{ Character(UnicodeScalar($0 + 96)!) }))
