Pravokutni

input/code.cpp: In function 'int main()':
input/code.cpp:50:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       for( int j = 0, k; j < rays.size(); j = k ) {
                          ~~^~~~~~~~~~~~~
input/code.cpp:54:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
          for( k = j; k < rays.size() && angle_eq( rays[j], rays[k] ); ++k ) 
                      ~~^~~~~~~~~~~~~
input/code.cpp:25:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf( "%d", &n );
    ~~~~~^~~~~~~~~~~~
input/code.cpp:26:38: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    for( int i = 0; i < n; ++i ) scanf( "%d%d", &x[i], &y[i] );
                                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

#include <algorithm>
#include <cstdio>
#include <vector>

using namespace std;

#define MAX 1500

struct ray {
   long long dx, dy;
   int quadrant;

   void rotate90() {
      long long tmp = dx; dx = dy; dy = -tmp;
      quadrant = (quadrant+1)%4;
   }
};
bool angle_lt ( const ray &A, const ray &B ) { return A.dy*B.dx <  B.dy*A.dx; }
bool angle_eq ( const ray &A, const ray &B ) { return A.dy*B.dx == B.dy*A.dx; }

int n;
int x[MAX], y[MAX];

int main( void ) {
   scanf( "%d", &n );
   for( int i = 0; i < n; ++i ) scanf( "%d%d", &x[i], &y[i] );

   int solution = 0;

   for( int i = 0; i < n; ++i ) {

      vector<ray> rays;

      for( int j = 0; j < n; ++j ) {
         if( i == j ) continue;

         ray R;
         R.quadrant = 0;
         R.dx = x[j]-x[i];
         R.dy = y[j]-y[i];

         while( !(R.dx > 0 && R.dy >= 0) ) R.rotate90();
         
         rays.push_back( R );
      }

      sort( rays.begin(), rays.end(), angle_lt ); 
      
      int count[4];
      for( int j = 0, k; j < rays.size(); j = k ) {

         count[0] = count[1] = count[2] = count[3] = 0;

         for( k = j; k < rays.size() && angle_eq( rays[j], rays[k] ); ++k ) 
            ++count[rays[k].quadrant];
         
         solution += count[0] * count[1];
         solution += count[1] * count[2];
         solution += count[2] * count[3];
         solution += count[3] * count[0];
      }
   }

   printf( "%d\n", solution );

   return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED