c++ whats wrong with this program?

#include <iostream>

#include <iomanip>

#include <cmath>

using namespace std;

struct Point

{

int x;

int y;

};

struct Triangle

{

Point pointA;

Point pointB;

Point pointC;

};

double distance(Point, Point);

int main()

{

const int NUM_TRIANGLES = 3;

Triangle members[NUM_TRIANGLES];

for (int index = 0; index < NUM_TRIANGLES; index++)

{

cout << "Enter x and y coordinates for point A in triangle " << (index + 1) << ": ";

cin >> members[index].pointA.x >> members[index].pointA.y;

cout << "Enter x and y coordinates for point B in triangle " << (index + 1) << ": ";

cin >> members[index].pointB.x >> members[index].pointB.y;

cout << "Enter x and y coordinates for point C in triangle " << (index + 1) << ": ";

cin >> members[index].pointC.x >> members[index].pointC.y;

}

for (int index = 0; index < NUM_TRIANGLES; index++)

{

double A = distance(members[index].pointA, members[index].pointB);

double B = distance(members[index].pointB, members[index].pointC);

double C = distance(members[index].pointC, members[index].pointA);

double perimeter = A + B + C;

cout << "Perimeter of Triangle " << (index + 1) << ": ";

cout << fixed << showpoint << setprecision(2) << perimeter;

cout << endl;

}

system("pause");

return 0;

}

double distance(Point point1, Point point2)

{

double x_diff = point2.x - point1.

double y_diff = point2.y

double side = sqrt(pow(x_diff, 2.0) + pow(y_diff, 2.0));

return side;

}