#include "bits/stdc++.h"
using namespace std;
#define fastcin {\
    cin.tie(0);\
    ios::sync_with_stdio(false);\
}
#define rep(i, a, b) for(int i = a; i < b; i++)
#define rrep(i, a, b) for(int i = a; i >= b; i--)
#define fore(i, a) for(auto &i:a)
#define print(x) cout << x << "\n"
#define SORT(a, n) sort(a, a+n);
#define REVERSE(a,n) reverse(a,a+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VREVERSE(v) reverse(v.begin(), v.end());
#define MOD 1000000007
#define yes "YES"
#define no "NO"
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;

int main() {
    fastcin;
    ll n, x=0, y;
    char a;
    cin >> n;
    int i;
    for(i=0; x<=n; i++) x+=pow(26, i+1);
    rrep(j, i, 1) {
        x = pow(26, j-1);
        a = 'A'+n/x-1;
        n %= x;
        if(j==1) {
            a++;
        }
        printf("%c", a);
    }
    printf("\n");
    return 0;
}