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Cod sursa(job #687045)
#include<cstdio>
#include<vector>
#include<algorithm>
#define MOD 95617
using namespace std;
struct per{int x, y;};
vector <per> h[MOD], v;
inline int H(int x, int y){
return abs((3 * x + 7 * y) % MOD);
}
bool Is(int x, int y){
int i, ind = H(x, y);
for (i = 0; i < (int) h[ind].size(); i++)
if (h[ind][i].x == x && h[ind][i].y == y) return true;
return false;
}
int main(){
int n, i, j, N, x, y, x1, x2, y1, y2;
freopen("patrate3.in", "r", stdin), freopen("patrate3.out", "w", stdout);
scanf ("%d", &n);
for (i = 0; i < n; i++){
scanf("%d.%d %d.%d", &x1, &y1, &x2, &y2);
x = x1 * 10000 + y1, y = x2 * 10000 + y2;
v.push_back((per) {x, y});
h[H(x, y)].push_back ((per) {x, y});
}
for (i = 0, N = 0; i < n; i++)
for (j = 0; j < n; j++)
if (i != j){
x1 = v[i].x + v[i].y - v[j].y;
y1 = v[i].y - v[i].x + v[j].x;
x2 = v[j].x - v[j].y + v[i].y;
y2 = v[j].x + v[j].y - v[i].x;
if (Is(x1, y1) && Is(x2, y2)) N++;
}
printf("%d", N / 4);
return 0;
}