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  1. #include <bits/stdc++.h>
  2. typedef long long ll;
  3. using namespace std;
  4. void Code_By_Mohamed_Khaled() {
  5.     ios_base::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.     cout.tie(nullptr);
  8. }
  9. ll Sum_of_range(ll l, ll r) {
  10.     if (l > r) return 0;
  11.     return r * (r + 1) / 2 - l * (l - 1) / 2;
  12. }
  13. ll mod = 1e9 + 7;
  14. ll add(ll a, ll b) { return ((b % mod) + (a % mod)) % mod; }
  15. ll mul(ll a, ll b) { return ((b % mod) * (a % mod)) % mod; }
  16. ll fast_power(ll x,ll y,ll mod)
  17. {
  18.     ll res=1;
  19.     x=x%mod;
  20.     if (x==0) return 0;
  21.     while (y > 0)
  22.     {
  23.         if (y & 1)res=(res*x)%mod;
  24.         y=y>>1;
  25.         x=(x*x)%mod;
  26.     }
  27.     return res;
  28. }
  29. ll nCr(ll n, ll r)
  30. {
  31.     if (r > n)return 0;
  32.     r = min(r, n - r);
  33.     ll x=1,y=1;
  34.     for (ll i = 0; i < r; i++) {
  35.         x=(x*((n-i)%mod))%mod;
  36.         y=(y*(i+1))%mod;
  37.     }
  38.     ll inv=fast_power(y,mod-2,mod);
  39.     return (x*inv)%mod;
  40. }
  41. int main() {
  42. #ifndef ONLINE_JUDGE
  43.     freopen("input.txt","r",stdin);
  44.     freopen("output.txt","w",stdout);
  45. #endif
  46.     Code_By_Mohamed_Khaled();
  47.     ll n,a,b;cin>>n>>a>>b;
  48.     ll ans=(fast_power(2,n,mod)-1-nCr(n,a)-nCr(n,b)+3*mod)%mod;
  49.     cout<<ans;
  50.     return 0;
  51. }
Success #stdin #stdout 0.01s 5288KB
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111751485
https://ideone.com/EOvGVX
language:
C++ (gcc 8.3)
created:
15 days ago
visibility:
public

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