Language: C++

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

int main()
{
  long long int n, m;
  cin >> n >> m;
  vector<pair<long long int, long long int>> vec(n);
  long long int a,b;
  for(long long int i = 0; i < n; i++) {
    cin >> a >> b;
    vec.at(i) = (a, b);
  }
  sort(vec.begin(), vec.end());
  long long int ans =0;
  lobg long int i = 0;
  while(true) {
    if(vec.at(i).first <= m) {
      ans += vec.at(i).first * vec.at(i).second;
      m -= vec.at(i).first;
      i++;
    }
    else if(m > 0 && vec.at(i).first >= m) {
      ans += m * vec.at(i).second;
      m -= vec.at(i).first;
      i++;
      break;
    }
    if(m == 0)
      break;
  }
  cout << ans << endl;
    
  
  
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:22: error: no match for 'operator=' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} and 'long long int')
   13 |     vec.at(i) = (a, b);
      |                      ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_pair.h:946:9: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, const _U1&>, std::is_assignable<_T2&, const _U2&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(const std::pair<_U1, _U2>&) [with _U2 = _U1; _T1 = long long int; _T2 = long long int]'
  946 |         operator=(const pair<_U1, _U2>& __p)
      |         ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:946:9: note:   template argument deduction/substitution failed:
a.cc:13:22: note:   mismatched types 'const std::pair<_T1, _T2>' and 'long long int'
   13 |     vec.at(i) = (a, b);
      |                      ^
/usr/include/c++/14/bits/stl_pair.h:957:9: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, _U1&&>, std::is_assignable<_T2&, _U2&&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(std::pair<_U1, _U2>&&) [with _U2 = _U1; _T1 = long long int; _T2 = long long int]'
  957 |         operator=(pair<_U1, _U2>&& __p)
      |         ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:957:9: note:   template argument deduction/substitution failed:
a.cc:13:22: note:   mismatched types 'std::pair<_T1, _T2>' and 'long long int'
   13 |     vec.at(i) = (a, b);
      |                      ^
/usr/include/c++/14/bits/stl_pair.h:921:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::__conditional_t<((bool)std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value), const std::pair<_T1, _T2>&, const std::__nonesuch&>) [with _T1 = long long int; _T2 = long long int; std::__conditional_t<((bool)std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value), const std::pair<_T1, _T2>&, const std::__nonesuch&> = const std::pair<long long int, long long int>&]'
  921 |       operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:923:65: note:   no known conversion for argument 1 from 'long long int' to 'std::__conditional_t<true, const std::pair<long long int, long long int>&, const std::__nonesuch&>' {aka 'const std::pair<long long int, long long int>&'}
  921 |       operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  922 |                                        is_copy_assignable<_T2>>::value,
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  923 |                                 const pair&, const __nonesuch&> __p)
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_pair.h:931:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::__conditional_t<((bool)std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value), std::pair<_T1, _T2>&&, std::__nonesuch&&>) [with _T1 = long long int; _T2 = long long int; std::__conditional_t<((bool)std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value), std::pair<_T1, _T2>&&, std::__nonesuch&&> = std::pair<long long int, long long int>&&]'
  931 |       operator=(__conditional_t<__and_<is_move_assignable<_T1>,
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:933:55: note:   no known conversion for argument 1 from 'long long int' to 'std::__conditional_t<true, std::pair<long long int, long long int>&&, std::__nonesuch&&>' {aka 'std::pair<long long int, long long int>&&'}
  931 |       operator=(__conditional_t<__and_<is_move_assignable<_T1>,
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  932 |                                        is_move_assignable<_T2>>::value,
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  933 |                                 pair&&, __nonesuch&&> __p)
      |                                 ~~~~~~~~~~~~~~~~~~~~~~^~~
a.cc:17:3: error: 'lobg' was not declared in this scope; did you mean 'long'?
   17 |   lobg long int i = 0;
      |   ^~~~
      |   long
a.cc:19:15: error: 'i' was not declared in this scope
   19 |     if(vec.at(i).first <= m) {
      |               ^