Language: C++

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

int main() {
  int n=0;
  cin>>n;
  vector<vector<int>> ent(vector<int>(3),n);
  vector<vector<int>> dp(vector<int>(3),n);
  for(int i=0;i<n;i++) {
    cin>>ent[i][0]>>ent[i][1]>>ent[i][2];
  }
  if(n==1) {
  	cout<<ent[0][getMax(ent[0])[0]]<<endl;
    return 0;
  }
  dp[0]=ent[0];
  for(int i=1;i<n;i++) {
    dp[i][0]=ent[i][0]+max(dp[i-1][1],dp[i-1][2]);
    dp[i][1]=ent[i][1]+max(dp[i-1][0],dp[i-1][2]);
    dp[i][2]=ent[i][2]+max(dp[i-1][1],dp[i-1][0]);
  }
  cout<<max(dp[n-1])<<endl;
  return 0;
}

Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'namespaces'
    2 | using namespaces std;
      |       ^~~~~~~~~~
a.cc: In function 'int main()':
a.cc:6:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |   cin>>n;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:7:3: error: 'vector' was not declared in this scope
    7 |   vector<vector<int>> ent(vector<int>(3),n);
      |   ^~~~~~
a.cc:7:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:7:17: error: expected primary-expression before 'int'
    7 |   vector<vector<int>> ent(vector<int>(3),n);
      |                 ^~~
a.cc:8:17: error: expected primary-expression before 'int'
    8 |   vector<vector<int>> dp(vector<int>(3),n);
      |                 ^~~
a.cc:10:10: error: 'ent' was not declared in this scope; did you mean 'int'?
   10 |     cin>>ent[i][0]>>ent[i][1]>>ent[i][2];
      |          ^~~
      |          int
a.cc:13:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   13 |         cout<<ent[0][getMax(ent[0])[0]]<<endl;
      |         ^~~~
      |         std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:13:15: error: 'ent' was not declared in this scope; did you mean 'int'?
   13 |         cout<<ent[0][getMax(ent[0])[0]]<<endl;
      |               ^~~
      |               int
a.cc:13:22: error: 'getMax' was not declared in this scope
   13 |         cout<<ent[0][getMax(ent[0])[0]]<<endl;
      |                      ^~~~~~
a.cc:13:42: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 |         cout<<ent[0][getMax(ent[0])[0]]<<endl;
      |                                          ^~~~
      |                                          std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:16:3: error: 'dp' was not declared in this scope; did you mean 'dup'?
   16 |   dp[0]=ent[0];
      |   ^~
      |   dup
a.cc:16:9: error: 'ent' was not declared in this scope; did you mean 'int'?
   16 |   dp[0]=ent[0];
      |         ^~~
      |         int
a.cc:18:24: error: 'max' was not declared in this scope; did you mean 'std::max'?
   18 |     dp[i][0]=ent[i][0]+max(dp[i-1][1],dp[i-1][2]);
      |                        ^~~
      |                        std::max
In file included from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: 'std::max' declared here
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
a.cc:22:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   22 |   cout<<max(dp[n-1])<<endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:22:9: error: 'max' was not declared in this scope; did you mean 'std::max'?
   22 |   cout<<max(dp[n-1])<<endl;
      |         ^~~
      |         std::max
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: 'std::max' declared here
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
a.cc:22:23: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   22 |   cout<<max(dp[n-1])<<endl;
      |                       ^~~~
      |                       std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~