1. //Bismillahir Rahmanir Rahim
2. #include<bits/stdc++.h>
3. #define ull unsigned long long
4. #define ll long long
5. #define pb push_back
6. #define mp make_pair
7. #define pob pop_back
8. #define in insert
9. #define vi vector<ll int>
10. #define vs vector<string>
11. #define pii pair<ll int,ll int>
12. #define psi pair<string,ll int>
13. #define pis pair<ll int,string>
14. #define mii map<ll int,ll int>
15. #define mib map<ll int,bool>
16. #define msi map<string,ll int>
17. #define mis map<ll int,string>
18. #define S string
19. #define fi first
20. #define se second
21. #define sp ' '
22. #define dl "\n"
23. #define all(data) data.begin(),data.end()
24. #define b() begin()
25. #define e() end()
26. #define cY cout<<"YES\n"
27. #define cN cout<<"NO\n"
28. #define cy cout<<"Yes\n"
29. #define cn cout<<"No\n"
30. #define setp(n) setprecision(n)
31. #define mem(arr,val) memset(arr,val,sizeof(arr));
32. #define debug(x) cerr<<x<<dl;
33. #define here fprintf(stderr, "====I am Here====\n");
34. #define FOR(data) for(auto it=data.begin();it!=data.end();it++)
35. #define Boost ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
36. #define maxx 100005
37. #define EPS 1e-9
38. #define setp(n) setprecision(n)
39. using namespace std;
40. const double PI = acos(-1);
41. ll int hp = 1e9+7;
42.  
43.  
44.  
45.  
46. void Boom()
47. {
48.     //Let's Move
49.  
50.    
51.     ll int x1,x2,x3,y1,y2,y3;
52.     cin>>x1>>y1>>x2>>y2>>x3>>y3;
53.  
54.     cout<<fixed<<setp(10)<<abs(x1*(y2 - y3) - y1*(x2 - x3) + (x2*y3 - y2*x3))/2.0<<dl;
55.  
56.  
57.  
58.  
59. }
60.  
61. int main()
62. {
63.     Boost;
64.     freopen("area1.in", "r", stdin);
65.     freopen("area1.out", "w", stdout);
66.  
67.  
68.     int t=1;     //  cin>>t;
69.     for(int i=1;i<=t;i++)
70.     {
71.         //cout<<"Case "<<i<<" : ";
72.         Boom();
73.     }
74.  
75.     return 0;
76.  
77. }
78.