inverse_mod_process_01

ll fact[N];
ll powerMod(ll a, ll b)
{
   if (b == 0)
       return 1;


   if (b % 2 == 0)
   {
       ll x = powerMod(a, b / 2);
       return (x * x) % mod;
   }
   else
   {
       ll x = powerMod(a, b / 2);
       return ((x * x) % mod * a) % mod;
   }


   return 0;
}


ll inverseMod(ll a)
{
   return powerMod(a, mod - 2);
}


ll nCrMod(ll n, ll r)
{
   if (r == 0)
       return 1;
   if (r > n)
       return 0;


   return (fact[n] * inverseMod((fact[r] * fact[n - r]) % mod)) % mod;
}
void factorial()
{
   fact[0] = 1;
   for (int i = 1; i < N; i++)
   {
       fact[i] = (fact[i - 1] * i) % mod;
   }
}