Toolkit 66Signs Have No Effect on the Parity∣ ∣ ∣a∣−∣b∣+∣c∣−∣d∣ ∣ ∣≡a+b+c+d(mod2)\bigl|\,|\,|a|-|b|+|c|-|d|\,|\,\bigr|\equiv a+b+c+d\pmod{2}∣∣a∣−∣b∣+∣c∣−∣d∣∣≡a+b+c+d(mod2)Related ProblemsMinorAIME I 2025 (Problem 5)