#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define p(s) cout<<(s)<<endl
#define REP(i,n,N) for(int i=n;i<N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=n;i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;

ll N;
string ans;
int main(){
    cin>>N;
    ans += 'A'+ N%26;
    N/=26;
    while(N>0){
        N--;
        ans += 'A' + N%26;
        N/=26;
    }
    RREP(i,0,ans.size()){
        cout<<ans[i];
    }
    cout<<endl;
    return 0;
}