Language: C++

#include<iostream>
#include<algorithm>
#include<vector>
#include<cmath>
#include<tuple>
using namespace std;
  
int main()
{
  int N, M; // 店舗数, 必要な本数
  cin >> N >> M;

  vector<tuple<long, long>> shops;
  long a, b;
  for( int i = 0; i < N; i++ ){
    cin >> a >> b;
    shops.push_back(make_tuple(a, b)); // (価格, 本数)
  }
  
  sort(shops.begin(), shops.end(), 
       //[](tuple<int, int> const &x, tuple<int, int> const &y) 
       [](auto &x, auto &y) 
       { return get<0>(x) < get<0>(y); } // 降順
      );

  //for( auto it = shops.begin(); it < shops.end(); it++ ){
    //cout << get<0>(*it) << " " << get<1>(*it) << endl;
  //}
  
  long sum = 0;
  long n;
  for( auto it = shops.begin(); it < shops.end(); it++ ){
    n = min(M, get<1>(*it));
    sum += get<0>(*it) * n;
    M -= n;
    if( M <= 0 ){ break; }
  }
  
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:33:12: error: no matching function for call to 'min(int&, std::__tuple_element_t<1, std::tuple<long int, long int> >&)'
   33 |     n = min(M, get<1>(*it));
      |         ~~~^~~~~~~~~~~~~~~~
In file included 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_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:33:12: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'std::__tuple_element_t<1, std::tuple<long int, long int> >' {aka 'long int'})
   33 |     n = min(M, get<1>(*it));
      |         ~~~^~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:33:12: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   33 |     n = min(M, get<1>(*it));
      |         ~~~^~~~~~~~~~~~~~~~