#include <iostream>
#include <algorithm>
using namespace std;

typedef long long ll;
int main() {
    ll n;
    cin >> n;
    string ans = "";
    int idx = 0;
    while(true) {
        if(idx !=0)
            n--;
        ans += char(n %  26 + 'A');
        n /= 26;
        if(n == 0)
            break;
        idx++;
    }
    for(int i=ans.size()-1;i>=0;i--)
        cout << ans[i];
    cout << endl;
}