#include <iostream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

#define FOR(x,y) for(int x = 0;x < y;x++)
#define LLI long long int

template<int um> class UF {
public:
    vector<int> par,rank,cnt;
    UF() {par=rank=vector<int>(um,0); cnt=vector<int>(um,1); for(int i=0;i<um;i++) par[i]=i;}
    void reinit() {FOR(i,um) rank[i]=0,cnt[i]=1,par[i]=i;}
    int operator[](int x) {return (par[x]==x)?(x):(par[x] = operator[](par[x]));}
    int count(int x) { return cnt[operator[](x)];}
    int operator()(int x,int y) {
        if((x=operator[](x))==(y=operator[](y))) return x;
        cnt[y]=cnt[x]=cnt[x]+cnt[y];
        if(rank[x]>rank[y]) return par[x]=y;
        rank[x]+=rank[x]==rank[y]; return par[y]=x;
    }
};

int main(int argc, const char * argv[]) {
    LLI N;
    cin >> N;

    vector<char> texts;
    while(N > 0)
    {
        int mod = N % 26;
        texts.push_back('A' + mod);
        N /= 26;
    }
    reverse(texts.begin(),texts.end());
    for(auto c : texts){
        cout << c;
    }
    cout << endl;
    return 0;
}