#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

int main() {
    int sz=1;
    LL sum=26;
    LL N;cin>>N;
    while(N>=sum){
        N-=sum;
        sum*=26;
        sz++;
    }
    string res;
    while(sz--){
        res+='A'+N%26;
        N/=26;
    }
    reverse(res.begin(),res.end());
    cout<<res<<endl;
}