unittest
{
	assert( [ "2" ].solve == "b" );
	assert( [ "27" ].solve == "aa" );
	assert( [ "123456789" ].solve == "jjddja" );
}



import std.algorithm;
import std.conv;
import std.range;
import std.stdio;

void main()
{
	stdin.byLineCopy.solve.writeln;
}

auto solve( Range )( Range input )
if( isInputRange!Range && is( ElementType!Range == string ) )
{
	auto n = input.front.to!( long );
	
	n--;
	auto ans = "";
	while( 0 <= n )
	{
		ans ~= cast( char )( 'a' + n % 26 );
		n = n / 26 - 1;
	}
	return ans.retro.array;
}
