Language: C++

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef long long ll;
int main() {
  int N, L;
  cin >> N >> L;
  vector<string> S(N);
  rep (int i, N) cin >> S.at(i);
  sort(S.begin(), S.end());
  rep (int i, N-1) cout << S.at(i);
  cout << S.at(N-1) << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:3:24: error: two or more data types in declaration of 'i'
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                        ^~~
a.cc:9:3: note: in expansion of macro 'rep'
    9 |   rep (int i, N) cin >> S.at(i);
      |   ^~~
a.cc:3:37: error: expected initializer before '<' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                     ^
a.cc:9:3: note: in expansion of macro 'rep'
    9 |   rep (int i, N) cin >> S.at(i);
      |   ^~~
a.cc:3:37: error: expected ';' before '<' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                     ^
a.cc:9:3: note: in expansion of macro 'rep'
    9 |   rep (int i, N) cin >> S.at(i);
      |   ^~~
a.cc:3:37: error: expected primary-expression before '<' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                     ^
a.cc:9:3: note: in expansion of macro 'rep'
    9 |   rep (int i, N) cin >> S.at(i);
      |   ^~~
a.cc:3:47: error: expected ')' before ';' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                       ~                       ^
a.cc:9:3: note: in expansion of macro 'rep'
    9 |   rep (int i, N) cin >> S.at(i);
      |   ^~~
a.cc:3:50: error: expected initializer before '++' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                                  ^~
a.cc:9:3: note: in expansion of macro 'rep'
    9 |   rep (int i, N) cin >> S.at(i);
      |   ^~~
a.cc:3:24: error: two or more data types in declaration of 'i'
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                        ^~~
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep (int i, N-1) cout << S.at(i);
      |   ^~~
a.cc:3:37: error: expected initializer before '<' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                     ^
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep (int i, N-1) cout << S.at(i);
      |   ^~~
a.cc:3:37: error: expected ';' before '<' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                     ^
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep (int i, N-1) cout << S.at(i);
      |   ^~~
a.cc:3:37: error: expected primary-expression before '<' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                     ^
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep (int i, N-1) cout << S.at(i);
      |   ^~~
a.cc:3:47: error: expected ')' before ';' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                       ~                       ^
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep (int i, N-1) cout << S.at(i);
      |   ^~~
a.cc:3:50: error: expected initializer before '++' token
    3 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                                  ^~
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep (int i, N-1) cout << S.at(i);
      |   ^~~