dobri

#include <bits/stdc++.h>

#define i64 long long
#define u64 unsigned long long
#define i32 int
#define u32 unsigned int

#define pii pair<int, int>
#define pll pair<long long, long long>

#define ld long double
#define defmod 1000000007

#define mati64(a,b) vector<vector<i64>>(a, vector<i64>(b, 0));
using namespace std;

int lul[606060];
int lis = 300000;
int main(){
  cin.sync_with_stdio(0);
  cin.tie(0);

  int n; cin >> n;
  int a[5050];
  for(int i = 0; i < n; ++i)
    cin >> a[i];
  unordered_set<int> lel;
  
  int ans = 0;
  lul[a[0]*2+lis] = 1;
  for(int i = 1; i < n; ++i){
    for(int j = 0; j < i; ++j){
      if(lul[a[i]-a[j]+lis]){
	++ans;
	break;
      }
    }
    lul[a[i]*2+lis] = 1;
    for(int j = 0; j < i; ++j){
      lul[a[i]+a[j]+lis] = 1;
    }
      
  }
  cout << ans << endl;
  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

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED