Language: C++

#include <bits/stdc++.h>
 
#define ll long long
 
using namespace std;
 
int main(){
   int N; cin >> N;
   int nb[52][52];
   ll ans = 0;
   memset(nb, 0, sizeof nb);
   vector<pair<int,int>> v;
   for (int i = 0; i < N; i++) {
      string d; cin >> d;
      ll num = llround(d*1e9);
      int a, b; a = b = 0;
      while (num%2 == 0) {
         num/= 2;
         a++;
      }
      while (num%5 == 0) {
         num/= 5;
         b++;
      }
      v.push_back({a,b});
      for (int j = 0; j <= a; j++) {
         for (int k = 0; k <= b; k++) {
            nb[j][k]++;
         }
      }
   }
   for (int i = 0; i < N; i++) {
      int a = v[i].first, b = v[i].second;
      ans+= nb[max(18-a,0)][18-b];
      if (a > 8 && b > 8)
         ans--;
   }
   cout << ans/2;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:25: error: no match for 'operator*' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'double')
   15 |       ll num = llround(d*1e9);
      |                        ~^~~~
      |                        | |
      |                        | double
      |                        std::string {aka std::__cxx11::basic_string<char>}
In file included 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/complex:400:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const complex<_Tp>&)'
  400 |     operator*(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:400:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/complex:409:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const _Tp&)'
  409 |     operator*(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:409:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/complex:418:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const _Tp&, const complex<_Tp>&)'
  418 |     operator*(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:418:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   mismatched types 'const std::complex<_Tp>' and 'double'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'double'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'double'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   15 |       ll num = llround(d*1e9);
      |                          ^~~
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:15:26: note:   mismatched types 'const std::valarray<_Tp>' and 'double'
   15 |       ll num = llround(d*1e9);
      |                          ^~~