#include <iostream>
#include <string>
using namespace std;
int main()
{
    long n; cin>>n;
    string res(1, 'A'+n%26);
    n/=26;
    while (n>1) {
        res=string(1, (n-1)%26+'A')+res;
        n/=26;
    }
    cout<<res<<endl;
}