清北考前刷題day5早安

  /* C(n,k) */ #include<iostream> #include<cstdio> #include<cstring> #define ll long long #define N 1000007 #define M 1000000007 using namespace std; ll n,k,ans,cnt1,cnt0; ll inv[N]={1,1},fac[N]={1,

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