#include <bits/stdc++.h>
using namespace std;

long long n;

int main(){
    scanf("%lld", &n);
    string ans = "";
    while (n > 0){
        ans = (char) ((n-1)%26 + 'a') + ans;
        n = (n-1) / 26;
    }
    cout<<ans;
    return 0;
}
