Language: C++

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

int main() {
  int n, m;
  cin >> n >> m;
  vector<vector<int>> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a.at(i).size();
    for (int j = 0; j < (int)a.at(i).size(); j++) {
      cin >> a.at(i).at(j);
    }
  }
  int sum;
  int res = 0;
  for (int k = 1; k <= m; k++) {
    sum = 0;
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        if (a.at(i).at(j) == k) {
          sum++;
        }
      }
    }
    if (sum == n) {
      res++;
    }
  }
  cout << res << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:9: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'std::vector<int>::size_type' {aka 'long unsigned int'})
    9 |     cin >> a.at(i).size();
      |     ~~~ ^~ ~~~~~~~~~~~~~~
      |     |                  |
      |     |                  std::vector<int>::size_type {aka long unsigned int}
      |     std::istream {aka std::basic_istream<char>}
In file included 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,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to an rvalue of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'double&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'std::vector<int>::size_type' {aka 'long unsigned int'}
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: invalid conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'void*' [-fpermissive]
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
      |                        |
      |                        std::vector<int>::size_type {aka long unsigned int}
a.cc:9:24: error: cannot bind rvalue '(void*)(& a.std::vector<std::vector<int> >::at(((std::vector<std::vector<int> >::size_type)i)))->std::vector<int>::size()' to 'void*&'
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:7: note:   conversion of argument 1 would be ill-formed:
a.cc:9:24: error: invalid conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
    9 |     cin >> a.at(i).size();
      |            ~~~~~~~~~~~~^~
      |                        |