Language: C++

\#include<algorithm>//sort,二分探索,など
#include<bitset>//固定長bit集合
#include<cmath>//pow,logなど
#include<complex>//複素数
#include<deque>//両端アクセスのキュー
#include<functional>//sortのgreater
#include<iomanip>//setprecision(浮動小数点の出力の誤差)
#include<iostream>//入出力
#include<iterator>//集合演算(積集合,和集合,差集合など)
#include<map>//map(辞書)
#include<numeric>//iota(整数列の生成),gcdとlcm(c++17)
#include<queue>//キュー
#include<set>//集合
#include<stack>//スタック
#include<string>//文字列
#include<unordered_map>//イテレータあるけど順序保持しないmap
#include<unordered_set>//イテレータあるけど順序保持しないset
#include<utility>//pair
#include<vector>//可変長配列

using namespace std;
typedef long long ll;

//マクロ
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define REPD(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define FOR(i,a,b) for(ll i=(a);i<=(b);i++)
#define FORD(i,a,b) for(ll i=(a);i>=(b);i--)
#define ALL(x) (x).begin(),(x).end() //sortなどの引数を省略したい
#define SIZE(x) ((ll)(x).size()) //sizeをsize_tからllに直しておく
#define INF 1000000000000 //10^12
#define MOD 10000007 //10^9+7
#define PB push_back

template<typename T, typename U, typename Comp=less<>>
bool chmax(T& xmax, const U& x, Comp comp={}) {
    if(comp(xmax, x)) {
        xmax = x;
        return true;
    }
    return false;
}

template<typename T, typename U, typename Comp=less<>>
bool chmin(T& xmin, const U& x, Comp comp={}) {
    if(comp(x, xmin)) {
        xmin = x;
        return true;
    }
    return false;
}

ll gcd(ll a, ll b){
    if(a % b == 0){
        return(b);
    }
    else{
        return(gcd(b, a % b));
    }
}

//scanf("%lld", &);
//cin >> ;
//cout << ans << endl;

ll N, M, K, i, j, k, l, ans, cnt = 0;


int main(){
    ll data, A, B;
    long double b;

    cin >> A;
    cin >> b;
    B = b * 100.0; //少数を整数に

    cout << A * B / 100 << endl;

    return 0;
}

Compiler output:
a.cc:1:1: error: stray '\' in program
    1 | \#include<algorithm>//sort,二分探索,など
      | ^
a.cc:1:2: error: stray '#' in program
    1 | \#include<algorithm>//sort,二分探索,など
      |  ^
a.cc:1:3: error: 'include' does not name a type
    1 | \#include<algorithm>//sort,二分探索,など
      |   ^~~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:62,
                 from /usr/include/c++/14/bitset:49,
                 from a.cc:2:
/usr/include/c++/14/ext/type_traits.h:164:35: error: 'constexpr const bool __gnu_cxx::__is_null_pointer' redeclared as different kind of entity
  164 |   __is_null_pointer(std::nullptr_t)
      |                                   ^
/usr/include/c++/14/ext/type_traits.h:159:5: note: previous declaration 'template<class _Type> constexpr bool __gnu_cxx::__is_null_pointer(_Type)'
  159 |     __is_null_pointer(_Type)
      |     ^~~~~~~~~~~~~~~~~
/usr/include/c++/14/ext/type_traits.h:164:26: error: 'nullptr_t' is not a member of 'std'
  164 |   __is_null_pointer(std::nullptr_t)
      |                          ^~~~~~~~~
In file included from /usr/include/c++/14/bits/stl_pair.h:60,
                 from /usr/include/c++/14/bits/stl_algobase.h:64:
/usr/include/c++/14/type_traits:295:27: error: 'size_t' has not been declared
  295 |   template <typename _Tp, size_t = sizeof(_Tp)>
      |                           ^~~~~~
/usr/include/c++/14/type_traits:666:33: error: 'nullptr_t' is not a member of 'std'
  666 |     struct is_null_pointer<std::nullptr_t>
      |                                 ^~~~~~~~~
/usr/include/c++/14/type_traits:666:42: error: template argument 1 is invalid
  666 |     struct is_null_pointer<std::nullptr_t>
      |                                          ^
/usr/include/c++/14/type_traits:670:48: error: template argument 1 is invalid
  670 |     struct is_null_pointer<const std::nullptr_t>
      |                                                ^
/usr/include/c++/14/type_traits:674:51: error: template argument 1 is invalid
  674 |     struct is_null_pointer<volatile std::nullptr_t>
      |                                                   ^
/usr/include/c++/14/type_traits:678:57: error: template argument 1 is invalid
  678 |     struct is_null_pointer<const volatile std::nullptr_t>
      |                                                         ^
/usr/include/c++/14/type_traits:984:26: error: 'size_t' has not been declared
  984 |   template<typename _Tp, size_t _Size>
      |                          ^~~~~~
/usr/include/c++/14/type_traits:985:40: error: '_Size' was not declared in this scope
  985 |     struct __is_array_known_bounds<_Tp[_Size]>
      |                                        ^~~~~
/usr/include/c++/14/type_traits:985:46: error: template argument 1 is invalid
  985 |     struct __is_array_known_bounds<_Tp[_Size]>
      |                                              ^
/usr/include/c++/14/type_traits:1429:37: error: 'size_t' is not a member of 'std'
 1429 |     : public integral_constant<std::size_t, alignof(_Tp)>
      |                                     ^~~~~~
/usr/include/c++/14/type_traits:1429:57: error: template argument 1 is invalid
 1429 |     : public integral_constant<std::size_t, alignof(_Tp)>
      |                                                         ^
/usr/include/c++/14/type_traits:1429:57: note: invalid template non-type parameter
/usr/include/c++/14/type_traits:1438:37: error: 'size_t' is not a member of 'std'
 1438 |     : public integral_constant<std::size_t, 0> { };
      |                                     ^~~~~~
/usr/include/c++/14/type_traits:1438:46: error: template argument 1 is invalid
 1438 |     : public integral_constant<std::size_t, 0> { };
      |                                              ^
/usr/include/c++/14/type_traits:1438:46: note: invalid template non-type parameter
/usr/include/c++/14/type_traits:1440:26: error: 'std::size_t' has not been declared
 1440 |   template<typename _Tp, std::size_t _Size>
      |                          ^~~
/usr/include/c++/14/type_traits:1441:21: error: '_Size' was not declared in this scope
 1441 |     struct rank<_Tp[_Size]>
      |                     ^~~~~
/usr/include/c++/14/type_traits:1441:27: error: template argument 1 is invalid
 1441 |     struct rank<_Tp[_Size]>
      |                           ^
/usr/include/c++/14/type_traits:1442:37: error: 'size_t' is not a member of 'std'
 1442 |     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
      |                                     ^~~~~~
/usr/include/c++/14/type_traits:1442:65: error: template argument 1 is invalid
 1442 |     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
      |                                                                 ^
/usr/include/c++/14/type_traits:1442:65: note: invalid template non-type parameter
/usr/include/c++/14/type_traits:1446:37: error: 'size_t' is not a member of 'std'
 1446 |     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
      |                                     ^~~~~~
/usr/include/c++/14/type_traits:1446:65: error: template argument 1 is invalid
 1446 |     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
      |                                                                 ^
/usr/include/c++/14/type_traits:1446:65: note: invalid template non-type parameter
/usr/include/c++/14/type_traits:1451:32: error: 'size_t' was not declared in this scope
 1451 |     : public integral_constant<size_t, 0> { };
      |                                ^~~~~~
/usr/include/c++/14/type_traits:64:1: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
   63 | #include <bits/version.h>
  +++ |+#include <cstddef>
   64 | 
/usr/include/c++/14/type_traits:1451:41: error: template argument 1 is invalid
 1451 |     : public integral_constant<size_t, 0> { };
      |                                         ^
/usr/include/c++/14/type_traits:1451:41: note: invalid template non-type parameter
/usr/include/c++/14/type_traits:1453:26: error: 'size_t' has not been declared
 1453 |   template<typename _Tp, size_t _Size>
      |                          ^~~~~~
/usr/include/c++/14/type_traits:1454:23: error: '_Size' was not declared in this scope
 1454 |     struct extent<_Tp[_Size], 0>
      |                       ^~~~~
/usr/include/c++/14/type_traits:1454:32: error: template argument 1 is invalid
 1454 |     struct extent<_Tp[_Size], 0>
      |                                ^
/usr/include/c++/14/type_traits:1455:32: error: 'size_t' was not declared in this scope
 1455 |     : public integral_constant<size_t, _Size> { };
      |                                ^~~~~~
/usr/include/c++/14/type_traits:1455:32: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/c++/14/type_traits:1455:40: error: '_Size' was not declared in this scope
 1455 |     : public integral_constant<size_t, _Size> { };
      |                                        ^~~~~
/usr/include/c++/14/type_traits:1455:45: error: template argument 1 is invalid
 1455 |     : public integral_constant<size_t, _Size> { };
      |                                             ^
/usr/include/c++/14/type_traits:1455:45: error: template argument 2 is invalid
/usr/include/c++/14/type_traits:1457:42: error: 'size_t' has not been declared
 1457 |   template<typename _Tp, unsigned _Uint, size_t _Size>
      |                                          ^~~~~~
/usr/include/c++/14/type_traits:1458:23: error: '_Size' was not declared in this scope
 1458 |     struct extent<_Tp[_Size], _Uint>
      |                       ^~~~~
/usr/include/c++/14/type_traits:1458:36: error: template argument 1 is invalid
 1458 |     struct extent<_Tp[_Size], _Uint>
      |                                    ^
/usr/include/c++/14/type_traits:1463:32: error: 'size_t' was not declared in this scope
 1463 |     : public integral_constant<size_t, 0> { };
      |                                ^~~~~~
/usr/include/c++/14/type_traits:1463:32: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/c++/14/type_traits:1463:41: error: template argument 1 is invalid
 1463 |     : public integral_constant<size_t, 0> { };
      |                                         ^
/usr/include/c++/14/type_traits:1463:41: note: invalid template non-type parameter
/usr/include/c++/14/type_traits:1857:26: error: 'size_t' does not name a type
 1857 |       { static constexpr size_t __size = sizeof(_Tp); };
      |                          ^~~~~~
/usr/include/c++/14/type_traits:1857:26: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/c++/14/type_traits:1859:14: error: 'size_t' has not been declared
 1859 |     template<size_t _Sz, typename _Tp, bool = (_Sz <= _Tp::__size)>
      |              ^~~~~~
/usr/include/c++/14/type_traits:1859:48: error: '_Sz' was not declared in this scope
 1859 |     template<size_t _Sz, typename _Tp, bool = (_Sz <= _Tp::__size)>
      |                                                ^~~
/usr/include/c++/14/type_traits:1860:14: error: no default argument for '_Tp'
 1860 |       struct __select;
      |              ^~~~~~~~
/usr/include/c++/14/type_traits:1862:14: error: 'size_t' has not been declared
 1862 |     template<size_t _Sz, typename _Uint, typename... _UInts>
      |              ^~~~~~
/usr/include/c++/14/type_traits:1863:23: error: '_Sz' was not declared in this scope
 1863 |       struct __select<_Sz, _List<_Uint, _UInts...>, true>
      |                       ^~~
/usr/include/c++/14/type_traits:1863:57: error: template argument 1 is invalid
 1863 |       struct __select<_Sz, _List<_Uint, _UInts...>, true>
      |                                                         ^
/usr/include/c++/14/type_traits:1866:14: error: 'size_t' has not been declared
 1866 |     template<size_t _Sz, typename _Uint, typename... _UInts>
      |              ^~~~~~
/usr/include/c++/14/type_traits:1867:23: error: '_Sz' was not declared in this scope
 1867 |       stru