#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<math.h>
#include<bits/stdc++.h>
#include<stack>
#include<queue>
#include<list>
#include<vector>
#include<bitset>
#include<unordered_map>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
// #include "boost/algorithm/string.hpp"
#define fio ios_base::sync_with_stdio(false)
#define mod 998244353
#define mod1 mod
#define mod2 1000000007
#define li long long int
#define ll li
#define readi(x) scanf("%d",&x)
#define  reads(x)  scanf("%s", x)
#define readl(x) scanf("%I64d",&x)
#define rep(i,n) for(i=0;i<n;i++)
#define revp(i,n) for(i=(n-1);i>=0;i--)
#define myrep1(i,a,b) for(i=a;i<=b;i++)
#define myrep2(i,a,b) for(i=b;i>=a;i--)
#define pb push_back
#define mp make_pair
#define fi first
#define sec second
#define MAXN 1000000000010000005
#define MINN -1000000000000000000
#define INTMAX 1000001000
#define pii pair<ll,ll>
#define pdd pair<double,double>
#define pic pair<int,char>
#define N 3000105
#define lgn 20
#define ddouble long double
#define minus minu
#define PI 2*acos(0)
#define lgn 20
 
 
// #define INTMAX 200000000
 
// using namespace boost;
// #define si short int
 
using namespace std;
using namespace __gnu_pbds;
typedef priority_queue<pii, vector<pii > > max_pq;
typedef priority_queue<pii, vector<pii> , greater<pii>  > min_pq;
ll toint(const string &s) {stringstream ss; ss << s; ll x; ss >> x; return x;}
string tostring ( ll number ){stringstream ss; ss<< number; return ss.str();}
 
// using namespace __gnu_pbds;
// typedef priority_queue<pair<ll,char> , vector<pair<ll , char> > > max_pq;
// typedef priority_queue<pii , vector<pii > ,greater<pii > > min_pq;
typedef tree<pair<string,string> , null_type, less<pair<string,string> >, rb_tree_tag, tree_order_statistics_node_update> OST;
// typedef priority_queue<pair < ll , pair < pii , ll > >  , vector<pair < ll , pair < pii , ll > >  > ,greater<pair < ll , pair < pii , ll > >  > > min_pq;
#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
    template <typename Arg1>
    void __f(const char* name, Arg1&& arg1){
        cout << name << " : " << arg1 << std::endl;
        //use cerr if u want to display at the bottom
    }
    template <typename Arg1, typename... Args>
    void __f(const char* names, Arg1&& arg1, Args&&... args){
        const char* comma = strchr(names + 1, ','); cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
    }
#else
#define trace(...)
#endif
#define nn 2000005
ll ar[ N ];
ll po[ N ];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    ll vl = 1;
    po[0] = 1;
    for ( ll i= 1; i <= 12; i ++){
        vl = ( vl*26LL);
        po[i] = vl;
        ar[i] = (ar[i-1] + vl);
    }
    // trace(ar[12]);
    ll len = 0;
    ll n;
    cin >> n;
    for ( ll i = 1; i <= 12; i ++){
        if ( ar[i] >= n ){
            len = i;
            break;
        }
    }
    // trace(len);
    n -= ar[len-1];
    n -= 1;
    // trace(n);
    for ( ll i = 1; i <= len; i ++){
        if ( (n/po[(len-i)]) == 0 ){
            cout <<'a';
            continue;
        }
        cout << (char)('a' + ((n/po[(len-i)])));
        // trace(((n/po[(len-i)])-1));
        ll vl = po[len-i]*((n/po[(len-i)]));
        n -= vl;
    }
    
    
}


Measured memory_bytes: 3664