private static void WriteBond( TextWriter writer, Molecule molecule, int i) { int f = molecule.GetFirstInBond(i) + 1; int s = molecule.GetSecondInBond(i) + 1; int o = molecule.GetBondOrderAsInt(i); writer.Write($"{f,3:D}{s,3:D}{o,3:D} 0 0 0 0"); writer.Write('\n'); }