Language: C++

#include <bits/stdc++.h>
using namespace std;
#define MOD 1000000007
#define int long long
long long moduloMultiplication(long long a, long long b, long long mod) {
  long long res = 0;
  a %= mod;
  while (b) {
    if (b & 1)
      res = (res + a) % mod;
    a = (2 * a) % mod;
    b >>= 1; // b = b / 2
  }
  return res;
}

int32_t main() {
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
  freopen("output.txt", "w", stderr);
#endif
  int n;
  cin >> n;
  vector<int64_t> v(n);
  for (int i = 0; i < n; i++)
    cin >> v[i];
  int64_t arrSum = 0;
  for (int i = 0; i < n; i++)
    arrSum = (arrSum + v[i]);
  int64_t sq = arrSum * arrSum;
  int64_t ans = 0;
  int64_t tmp = 0;
  for (int i = 0; i < n; i++)#include <bits/stdc++.h>
using namespace std;
#define MOD 1000000007
#define int long long
long long moduloMultiplication(long long a, long long b, long long mod) {
  long long res = 0;
  a %= mod;
  while (b) {
    if (b & 1)
      res = (res + a) % mod;
    a = (2 * a) % mod;
    b >>= 1; // b = b / 2
  }
  return res;
}

int32_t main() {
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
  freopen("output.txt", "w", stderr);
#endif
  int n;
  cin >> n;
  vector<int64_t> v(n);
  for (int i = 0; i < n; i++)
    cin >> v[i];
  int64_t arrSum = 0;
  for (int i = 0; i < n; i++)
    arrSum = (arrSum + v[i]);
  int64_t sq = arrSum * arrSum;
  int64_t ans = 0;
  int64_t tmp = 0;
  for (int i = 0; i < n; i++)
    tmp = (tmp + (v[i] * v[i]));
  cout << ((sq - tmp) / 2) % MOD;
  return 0;
}
    tmp = (tmp + (v[i] * v[i]));
  cout << ((sq - tmp) / 2) % MOD;
  return 0;
}

Compiler output:
a.cc:34:30: error: stray '#' in program
   34 |   for (int i = 0; i < n; i++)#include <bits/stdc++.h>
      |                              ^
a.cc: In function 'int32_t main()':
a.cc:34:31: error: 'include' was not declared in this scope
   34 |   for (int i = 0; i < n; i++)#include <bits/stdc++.h>
      |                               ^~~~~~~
a.cc:34:40: error: 'bits' was not declared in this scope
   34 |   for (int i = 0; i < n; i++)#include <bits/stdc++.h>
      |                                        ^~~~
a.cc:34:45: error: 'stdc' was not declared in this scope; did you mean 'std'?
   34 |   for (int i = 0; i < n; i++)#include <bits/stdc++.h>
      |                                             ^~~~
      |                                             std
a.cc:35:1: error: expected primary-expression before 'using'
   35 | using namespace std;
      | ^~~~~
a.cc:38:73: error: a function-definition is not allowed here before '{' token
   38 | long long moduloMultiplication(long long a, long long b, long long mod) {
      |                                                                         ^
a.cc:50:13: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   50 | int32_t main() {
      |             ^~
a.cc:50:13: note: remove parentheses to default-initialize a variable
   50 | int32_t main() {
      |             ^~
      |             --
a.cc:50:13: note: or replace parentheses with braces to value-initialize a variable
a.cc:50:16: error: a function-definition is not allowed here before '{' token
   50 | int32_t main() {
      |                ^
a.cc:72:21: error: 'i' was not declared in this scope
   72 |     tmp = (tmp + (v[i] * v[i]));
      |                     ^