#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
main(){
    ll N;
    cin >> N;
    N++;
    string s;
    for(;N>=1;N/=26){
        char c = ((N+25)%26+'A');
        if(c == 'Z')N-=26;
        s = c + s;
    }
    cout << s << endl;
}