Combination Number

#define MX (1<<20)
#define MOD (1000000007)
ll f[MX]={1,1},I[MX]={1,1},J[MX]={1,1};
void pre(){FT(2,MX)f[k]=f[k-1]*k%MOD,J[k]=-MOD/k*J[MOD%k]%MOD+MOD,I[k]=I[k-1]*J[k]%MOD;;}
ll C(int N,int K){return N<K?0:(f[N]*I[K]%MOD)*I[N-K]%MOD;}