bool generation_function()
{
	int i, j, k;

	memset( res, false, sizeof(res[0])*(cash+1) );
	res[0] = true;
	for( i = 0; i < N; ++i )
	{
		for( j = cash-1; j >= 0; --j )
		{
			if( !res[j] )
				continue;
			int t = j;
			for( k = 0; k < can_use[i]; ++k )
			{
				t += D[i];
				if( t > cash )
					break;
				else if( t == cash )
					return true;
				else
					res[t] = true;
			}
		}
	}
	return false;
}