#include<bits/stdc++.h>
#define REP(x,y,z) for(int x=y;x<=z;x++)
#define FORD(x,y,z) for(int x=y;x>=z;x--)
#define MSET(x,y) memset(x,y,sizeof(x))
#define FOR(x,y) for(__typeof(y.begin()) x=y.begin();x!=y.end();x++)
#define F first
#define S second
#define MP make_pair
#define PB push_back
#define SZ size()
#define M 
void RI(){}
template<typename... T>
void RI( int& head, T&... tail ) {
    scanf("%d",&head);
    RI(tail...);
}
using namespace std;
typedef long long LL;
LL n;
LL cnt;
int ans[30];
int main()
{
	int alp;
	while(~scanf("%lld",&n))
	{
		alp=1;
		cnt=26;
		while(n>=cnt)
		{
			n -= cnt;
			cnt *= 26;
			alp++;
		}

		REP(i,1,alp)
		{
			ans[i] = n%26;
			n /= 26;
		}
		FORD(i,alp,1)
		{
			putchar('A'+ans[i]);
		}
		puts("");
	}
	return 0;
}