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  1.  
  2. #include<bits/stdc++.h>
  3. using namespace std;
  4. #define MOD 100-1  //NA
  5. #define ll long long int
  6. #define rep(i,a,b) for(int i=a;i<=(int)(b);i++)
  7.  
  8. ll n,rt,ans;
  9. ll arr[2005][2005],x[2005],y[2005];
  10. ll sqr[50000000+10];
  11. int main()
  12. {
  13. 	freopen("##inp.cpp","r",stdin);
  14.     //freopen("##out.cpp","w",stdout);
  15. 	//ios_base::sync_with_stdio(0);
  16. 	cin>>n;
  17. 	rep(i,0,n-1) cin>>x[i]>>y[i];
  18. 	if(n<3) {cout<<"0"; return 0;}
  19. 	rep(i,0,n-1)
  20. 	{
  21. 	    rep(j,i+1,n-1)
  22. 	    {
  23. 	        int a=x[j]-x[i],b=y[j]-y[i];
  24. 	        int cur=__gcd(a,b);
  25. 	        if(cur==0) {continue; rt++;}
  26. 	        a=a/cur; b=b/cur;
  27. 	        arr[a+500][b+500]++;
  28. 	    }
  29. 	}
  30. 	rep(i,0,3000) sqr[i*i]=i;
  31.  
  32.     ans=(n*(n-1)*(n-2))/6ll;
  33. 	//cout<<ans<<endl;
  34. 	rep(i,1,1000)rep(j,1,1000)
  35. 	{
  36. 	    ll cur=1+8ll*arr[i][j];
  37. 	    if(arr[i][j]==0) continue;
  38. 	    cur=(sqr[cur]+1)/2ll;
  39. 	    ans=ans-(cur*(cur-1)*(cur-2))/6ll;
  40. 	    //cc2(cur,ans);
  41. 	}
  42.     ll cur=1+8ll*rt;
  43.     cur=(sqrt(cur)+1)/2ll;
  44.     ans=ans-(cur*(cur-1)*(cur-2))/6ll;
  45.  
  46.     cout<<ans<<endl;
  47. }
  48.  
Success #stdin #stdout 0s 425216KB
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stdout 
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https://ideone.com/k8J9Zu
language:
C++ (gcc 8.3)
created:
9 years ago
visibility:
secret

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