#include<iostream>
#include<cstdio>
#define endl '\n'
using namespace std;
typedef  long long ll;
ll n,i,j,p,q,m,k;
int main()
{
    freopen("excel.in", "r", stdin);
    freopen("excel.out", "w", stdout);
    cin>>n;
    p = n;
    q=1;k=1;
    while(p>0)
    {
        q*=26;
        p-=q;
        k+=q;
    }
    k-=q;q/=26;
    k-=q;
    //cout<<k<<endl;
    while(n>0)
    {
        for(j=26;j>=1;j--)
        {
            if(n-j*q>=k)
            {
                cout<<(char)(j+'A'-1);
                n-=j*q;
                q/=26;
                k-=q;
                break;
            }
        }
    }
    return 0;
}
///17576