#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n) for(int(i)=0;(i)<(n);++(i))
#define in(T,V) T V;cin>>V;

int main(){
    in(ll,N);
    ll r = 1, v = 0;
    REP(i,10){
        r *= 26;
        if(N < r){ v = i; break; }
        N -= r;
    }
    string s;
    REP(i,v+1){
        s += ('A' + N % 26);
        N /= 26;
    }
    reverse(s.begin(), s.end());
    cout << s << endl;
}