import std.conv, std.stdio;
import std.algorithm, std.array, std.range, std.string;
enum p = 26;

void main()
{
    auto a = p;
    auto i = 1;
    auto n = readln.chomp.to!ulong - 1;
    while (a <= n)
    {
        n -= a;
        a *= p;
        i += 1;
    }
    n.to26ary(i).writeln;
}

private:

auto to26ary(ulong n, int i)
{
    string ret;
    foreach (_; 0..i)
    {
        ret = cast(char)('a' + (n % p)) ~ ret;
        n /= p;
    }
    return ret;
}
