#include<bits/stdc++.h>
using lint=long long;
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    lint x;std::cin>>x;
    x++;
    std::string s;
    while(x){
        lint y=x%26;
        if(y==0)y=26;
        s.push_back('A'+y-1);
        x-=y;
        x/=26;
    }
    std::cout<<std::string(s.rbegin(),s.rend())<<'\n';
}
/*
 * A -> 1
 * Z -> 26
 * AA -> 27 = 26 + 1
 * AZ -> 52
 * BA -> 53 = 52 + 1
 * ZZ -> 26 * 26 + 26
 * AAA -> 26 * 26 + 26 + 1
 */