Language: C++

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

using ll=long long;
const int inf=100000000;

int in(){
  int a;
  cin >> a;
  return a;
}//int型関数の受け取り

void forin(int* x,int y){
  for (int i=0;i<y;i++){
    cin >> x[i];
  }
}//(x,y) int型配列x[y]の受け取り

int intpow(int x,int y){
  double a=x,b=y;
  return pow(a,b);
}//(x,y) xをy乗

int intfabs(int x){
  double a=x;
  return fabs(a);
}//(x) xの絶対値

int fact(int x){
  if (x == 1) return 1;
  return x*fact(x-1);
}//(x) x!

int fib(int x){
  if (x <= 2) return x;
  int a[x];
  a[0]=1;
  a[1]=2;
  for (int i=2;i<x;i++){
    a[i]=a[i-1]+a[i-2];
  }
  return a[x-1];
}//(x) フィボナッチ数列のx番目

int div1(ll x){
  return x%1000000007;
}

main(){
    int n=in();
    vector<int> v(n);
    for (int i=0;i<n;i++) cin >> v[i];
    sort(v.begin,v.end);
    double pl=(v[0]+v[1])/2;
    for (int i=2;i<n;i++) pl=(pl+v[i])/2;
    cout << pl << endl;
}

Compiler output:
a.cc:49:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   49 | main(){
      | ^~~~
a.cc: In function 'int main()':
a.cc:53:9: error: no matching function for call to 'sort(<unresolved overloaded function type>, <unresolved overloaded function type>)'
   53 |     sort(v.begin,v.end);
      |     ~~~~^~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algo.h:4762:5: note: candidate: 'template<class _RAIter> void std::sort(_RAIter, _RAIter)'
 4762 |     sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
      |     ^~~~
/usr/include/c++/14/bits/stl_algo.h:4762:5: note:   template argument deduction/substitution failed:
a.cc:53:9: note:   couldn't deduce template parameter '_RAIter'
   53 |     sort(v.begin,v.end);
      |     ~~~~^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:4793:5: note: candidate: 'template<class _RAIter, class _Compare> void std::sort(_RAIter, _RAIter, _Compare)'
 4793 |     sort(_RandomAccessIterator __first, _RandomAccessIterator __last,
      |     ^~~~
/usr/include/c++/14/bits/stl_algo.h:4793:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:86:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:292:1: note: candidate: 'template<class _ExecutionPolicy, class _RandomAccessIterator, class _Compare> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, void> std::sort(_ExecutionPolicy&&, _RandomAccessIterator, _RandomAccessIterator, _Compare)'
  292 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp);
      | ^~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:292:1: note:   candidate expects 4 arguments, 2 provided
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note: candidate: 'template<class _ExecutionPolicy, class _RandomAccessIterator> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, void> std::sort(_ExecutionPolicy&&, _RandomAccessIterator, _RandomAccessIterator)'
  296 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last);
      | ^~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note:   candidate expects 3 arguments, 2 provided