#include <bits/stdc++.h>

using namespace std;

typedef long long lli;

int main()
{
    lli n; cin >> n;

    string table = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    
    string ans = "";

    do {
        ans = table[n % 26] + ans;
        n /= 26; n--;
    } while (~n);

    cout << ans << endl;
}