Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  int N;
  cin>>N;
  vector<int> vec(N);
  for (int i = 0; i < N; i++) {
    cin >> vec.at(i);
  }

  int a=0;
  for(int i=0; i<N;i++){
    for(int j=i+1; j<N;j++){
      for(int k=j+1; k<N;k++){
        if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
        a++;
      }
    }
  }
  cout <<a<<endl;
  
}

Compiler output:
a.cc: In function 'int main()':
a.cc:16:14: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |              ^~
a.cc:16:22: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                      ^~
a.cc:16:30: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                              ^~
a.cc:16:40: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                        ^~
a.cc:16:48: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                                ^~
a.cc:16:56: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                                        ^~
a.cc:16:66: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                                                  ^~
a.cc:16:74: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                                                          ^~
a.cc:16:82: error: request for member 'at' in 'N', which is of non-class type 'int'
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                                                                  ^~
a.cc:16:88: error: expected ')' before '{' token
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |                                     ~                                                  ^
      |                                                                                        )
a.cc:18:8: error: expected ')' before '}' token
   18 |       }
      |        ^
      |        )
   19 |     }
      |     ~   
a.cc:16:11: note: to match this '('
   16 |         if(N.at(i)<N.at(j)+N.at(k)&&(N.at(j)<N.at(i)+N.at(k)&&(N.at(k)<N.at(j)+N.at(i)){
      |           ^
a.cc:19:5: error: expected primary-expression before '}' token
   19 |     }
      |     ^
a.cc:23:2: error: expected '}' at end of input
   23 | }
      |  ^
a.cc:4:12: note: to match this '{'
    4 | int main() {
      |            ^