// yukicoder 327 (http://yukicoder.me/problems/904)
#include<cstdio>
#include<vector>
#define repd(i,a) for(int i=(a);i>=0;--i)

typedef long long ll;

ll N;

std::vector<ll> ts, vs;

ll powLL( ll x, ll n )
{
	ll ret = 1;

	for( ll i = 0; i < n; ++i )
		ret *= x;

	return ret;
}

int main()
{
	scanf( "%lld", &N );

	if( N <= 25 )
	{ putchar( 'A'+N ); puts(""); return 0; }	

	N -= 26;

	ll t = N;
	while( t > 0 )
		ts.push_back( t%26 ), t /= 26;

	if( ts.size() >= 3 ) repd( i, ts.size()-1 ) if( i >= 2 )
	{
		if( ts.size() >= 4 && i == ts.size()-1 && !ts[i-1] )
			continue;
		
		N -= powLL( 26, i );
	}

	while( N > 0 )
		vs.push_back( N%26 ), N /= 26;

	if( !( ts.size()>=4 && ts[ts.size()-1] == 1 && ts[ts.size()-2] == 0 ) ) while( vs.size() < 2 || vs.size() < ts.size() )
			vs.push_back( 0 );

	repd( i, vs.size()-1 )
		putchar( 'A'+vs[i] );

	puts("");

	return 0;
}