Method operator -

code/mathematics/ntt.cpp:10–10

  Num(ll _x=0) { x = (_x%mod+mod)%mod; }
  Num operator +(const Num &b) { return x + b.x; }
  Num operator -(const Num &b) const { return x - b.x; }
  Num operator *(const Num &b) const { return (ll)x * b.x; }
  Num operator /(const Num &b) const {
    return (ll)x * b.inv().x; }