#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
int main() {
    LL N;cin>>N;
    if(N==0){
        cout<<'A'<<endl;return 0;
    }
    string s;
    while(N){
        s+=('A'+(N%26-1));
        N/=26;
    }
    s[0]++;
    reverse(s.begin(),s.end());
    cout<<s<<endl;
    return 0;
}