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#include<iostream>
using namespace std;
int mian(){
    int x1, y1, x2, y2, x3, y3, A;
    while(cin>>x1>>y1>>x2>>y2>>x3>>y3>>A){
    A=abs(x1*y2+x2*y3+x3*y1-x2*y1-x3*y2-x1*y3)/2
    cout<<A/7<<endl;
    }
    return 0;
}  

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要「四捨五入到整數位」。 

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3q~~~~~