let alpha = 26
let alphabets = Array("abcdefghijklmnopqrstuvwxyz").map({String($0)})

var N = Int(readLine()!)!
var ans = ""

while N > 0 {
    if N % alpha == 0 {
        ans = "z" + ans
        N /= alpha
        N -= 1
    } else {
        ans = alphabets[N % alpha - 1] + ans
        N /= alpha
    }
}
print(ans)
