#include<bits/stdc++.h>
#include <atcoder/all>
#ifdef LOCAL
#include <debug_print.hpp>
#define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (static_cast<void>(0))
#endif
using namespace atcoder;
using mint=modint998244353;
using namespace std;
using ll=long long;
using ul=unsigned long long;
int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1};
int dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};
using Graph=vector<vector<int>>;
ll op(ll a,ll b){return min(a,b);}
ll e(){return 2e9;}
int main(){
    ll N;
    cin>>N;
    string S;
    if(N==0){cout<<"A"<<endl;return 0;}
    int cnt=0;
    while(N){
        if(cnt>0)N--;
        S+=N%26+'A',N/=26;
        cnt++;
    }
    
    reverse(S.begin(),S.end());
    cout<<S<<endl;
}