ChallengeMediumHard Number Theory ShareHard Number Theory · Medium problemHow many integers xxx with 0≤x<10000 \le x < 10000≤x<1000 satisfy x2≡1(mod1000)x^{2} \equiv 1 \pmod{1000}x2≡1(mod1000)?Check Show answer Walk through it step by step Practice more like this Review this concept