Language: C++

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fo(a,b) for(int a=0;a<b;a++)
 int $(int a,int b) {
   if(a%b==0)
     return a/b;
   else
     return a/b+1;
 }
 int keta(int a){
  double b=a;
  b=log10(b);
  int c=b;
  return c+1;
 }
 int souwa(int a){
  return a*(a+1)/2;
 }

signed main(){
  int a,b,e,f;
  cin>>a>>b;
  vector<int> c(a,0);
  vector<double> d(a);
  fo(i,a){
  e=i;
  f=0;
  if(i>=b)
    break;
  while(e>=b){
    e*=2;
    f++;
  }
  c.at(i)=f;
  }
  for(int i=0;i<a;i++){
    d.at(i)=pow(2,c);
    d.at(i)=1.0/d.at(i);
  }
  double g=0;
  fo(i,a)
  g+=d.at(i);
  cout<<g/a<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:38:16: error: no matching function for call to 'pow(int, std::vector<long long int>&)'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166,
                 from a.cc:1:
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_Constant, std::_ValArray, _Tp, _Tp>, _Tp> std::pow(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   'std::vector<long long int>' is not derived from 'const std::valarray<_Tp>'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_ValArray, std::_Constant, _Tp, _Tp>, _Tp> std::pow(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_ValArray, std::_ValArray, _Tp, _Tp>, _Tp> std::pow(const valarray<_Tp>&, const valarray<_Tp>&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename _Dom::value_type> std::pow(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   'std::vector<long long int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename _Dom::value_type> std::pow(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename _Dom::value_type> std::pow(const valarray<typename _Dom::valarray>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   'std::vector<long long int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename _Dom::value_type> std::pow(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::_Pow, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename _Dom1::value_type> std::pow(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  549 | _DEFINE_EXPR_BINARY_FUNCTION(pow, struct std::_Pow)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:549:1: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:2482:5: note: candidate: 'template<class _Tp, class _Up> std::complex<typename __gnu_cxx::__promote<decltype (((typename __gnu_cxx::__promote<_Tp, std::__is_integer<_Tp>::__value>::__type)(0) + (typename __gnu_cxx::__promote<_Up, std::__is_integer<_Up>::__value>::__type)(0)))>::__type> std::pow(const complex<_Tp>&, const complex<_Up>&)'
 2482 |     pow(const std::complex<_Tp>& __x, const std::complex<_Up>& __y)
      |     ^~~
/usr/include/c++/14/complex:2482:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/complex:2474:5: note: candidate: 'template<class _Tp, class _Up> std::complex<typename __gnu_cxx::__promote<decltype (((typename __gnu_cxx::__promote<_Tp, std::__is_integer<_Tp>::__value>::__type)(0) + (typename __gnu_cxx::__promote<_Up, std::__is_integer<_Up>::__value>::__type)(0)))>::__type> std::pow(const _Tp&, const complex<_Up>&)'
 2474 |     pow(const _Tp& __x, const std::complex<_Up>& __y)
      |     ^~~
/usr/include/c++/14/complex:2474:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   'std::vector<long long int>' is not derived from 'const std::complex<_Up>'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/complex:2466:5: note: candidate: 'template<class _Tp, class _Up> std::complex<typename __gnu_cxx::__promote<decltype (((typename __gnu_cxx::__promote<_Tp, std::__is_integer<_Tp>::__value>::__type)(0) + (typename __gnu_cxx::__promote<_Up, std::__is_integer<_Up>::__value>::__type)(0)))>::__type> std::pow(const complex<_Tp>&, const _Up&)'
 2466 |     pow(const std::complex<_Tp>& __x, const _Up& __y)
      |     ^~~
/usr/include/c++/14/complex:2466:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/complex:1339:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::pow(const _Tp&, const complex<_Tp>&)'
 1339 |     pow(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~
/usr/include/c++/14/complex:1339:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   'std::vector<long long int>' is not derived from 'const std::complex<_Tp>'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/complex:1328:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::pow(const complex<_Tp>&, const complex<_Tp>&)'
 1328 |     pow(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~
/usr/include/c++/14/complex:1328:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/complex:1294:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::pow(const complex<_Tp>&, const _Tp&)'
 1294 |     pow(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~
/usr/include/c++/14/complex:1294:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
/usr/include/c++/14/complex:1285:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::pow(const complex<_Tp>&, int)'
 1285 |     pow(const complex<_Tp>& __z, int __n)
      |     ^~~
/usr/include/c++/14/complex:1285:5: note:   template argument deduction/substitution failed:
a.cc:38:16: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   38 |     d.at(i)=pow(2,c);
      |             ~~~^~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:114:
/usr/include/c++/14/cmath:1074:5: note: candidate: 'template<class _Tp, class _Up> constexpr typename __gnu_cxx::__promote_2<_Tp, _Up>::__type std::pow(_Tp, _Up)'
 1074 |     pow(_Tp __x, _Up __y)
      |     ^~~
/usr/include/c++/14/cmath:1074:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/14/bits/stl_algobase.h:62,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/ext/type_traits.h: In substitution of 'template<class _Tp, class _Up> using __gnu_cxx::__promote_2 = __gnu_cxx::__promote<decltype ((