2019牛客多校（第一场）F-Random Point in Triangle

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
struct Point{
    ll x, y;
    Point( ll x=, ll y= ): x(x), y(y){}
};
typedef Point Vector;
Point p[];
Vector operator -(const Vector a, const Vector b ){
    return Vector( a.x-b.x, a.y-b.y );
}
 
ll Cross( Vector a, Vector b ){
    return a.x*b.y - a.y*b.x;
}
 
int main(){
    ios::sync_with_stdio();
    cin.tie();
    cout.tie();
    ll x1, y1, x2, y2, x3, y3;
    while( cin >> x1 >> y1 ){
        cin >> x2 >> y2 >> x3 >> y3;
        p[] = Point(x1, y1);
        p[] = Point(x2, y2);
        p[] = Point(x3, y3);
        ll ans = Cross( p[]-p[], p[]-p[] )*;
        if( ans< ) ans = -ans;
        cout << ans <<endl;
    }
 
    return ;
}