#include <iostream>
#include <string>
using namespace std;
int main()
{
    long n; cin>>n;
    string res;
    for(int i=0;n>-!i;++i) {
        if (i) --n;
        res=string(1, n%26+'A')+res;
        n/=26;
    }
    cout<<res<<endl;
}