Language: C++

        #include <vector>
        #include <list>
        #include <map>
        #include <set>
        #include <queue>
        #include <deque>
        #include <stack>
        #include <bitset>
        #include <algorithm>
        #include <functional>
        #include <numeric>
        #include <utility>
        #include <sstream>
        #include <iostream>
        #include <iomanip>
        #include <cstdio>
        #include <cmath>
        #include <cstdlib>
        #include <ctime>
        #include <string>
        #include <climits>
        #include <tuple>
        using namespace std;
        typedef long long ll;
        typedef pair<int,int> P;
        typedef tuple<int,int,int,int> T;
         
         
         
         
        int bit[100003],n;
        int sum(int i){
            int s=-1;
            while(i>0){
                s=max(bit[i],s);
                i-=i&-i;
            }
            return s;
        }
        void add(int i,int x){
            while(i<=n){
                bit[i]=max(bit[i],x);
                i+=i&-i;
            }
        }
        int main(){
            int a,b;
            cin>>a>>b;
            if((a+b)==15)cout<<'+'<<endl;
            else if ((a*b)==15) cout<<'*'<<endl;
            else cout<<'x'<endl;
            return 0;
        }

Compiler output:
a.cc: In function 'int main()':
a.cc:51:27: error: no match for 'operator<' (operand types are 'std::basic_ostream<char>' and '<unresolved overloaded function type>')
   51 |             else cout<<'x'<endl;
      |                  ~~~~~~~~~^~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/vector:62,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::pair<_T1, _T2>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/vector:66:
/usr/include/c++/14/bits/stl_vector.h:2089:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
 2089 |     operator<(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:2089:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::vector<_Tp, _Alloc>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/vector:87:
/usr/include/c++/14/tuple:2600:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator<(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2600 |     operator<(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2600:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::tuple<_UTypes ...>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/list:65,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_list.h:2188:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const __cxx11::list<_Tp, _Alloc>&, const __cxx11::list<_Tp, _Alloc>&)'
 2188 |     operator<(const list<_Tp, _Alloc>& __x, const list<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_list.h:2188:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::list<_Tp, _Alloc>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/map:63,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_map.h:1550:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const map<_Key, _Tp, _Compare, _Allocator>&, const map<_Key, _Tp, _Compare, _Allocator>&)'
 1550 |     operator<(const map<_Key, _Tp, _Compare, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:1550:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::map<_Key, _Tp, _Compare, _Allocator>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/map:64:
/usr/include/c++/14/bits/stl_multimap.h:1172:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const multimap<_Key, _Tp, _Compare, _Allocator>&, const multimap<_Key, _Tp, _Compare, _Allocator>&)'
 1172 |     operator<(const multimap<_Key, _Tp, _Compare, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_multimap.h:1172:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::multimap<_Key, _Tp, _Compare, _Allocator>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/set:63,
                 from a.cc:4:
/usr/include/c++/14/bits/stl_set.h:1025:5: note: candidate: 'template<class _Key, class _Compare, class _Alloc> bool std::operator<(const set<_Key, _Compare, _Allocator>&, const set<_Key, _Compare, _Allocator>&)'
 1025 |     operator<(const set<_Key, _Compare, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_set.h:1025:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::set<_Key, _Compare, _Allocator>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/set:64:
/usr/include/c++/14/bits/stl_multiset.h:1011:5: note: candidate: 'template<class _Key, class _Compare, class _Alloc> bool std::operator<(const multiset<_Key, _Compare, _Allocator>&, const multiset<_Key, _Compare, _Allocator>&)'
 1011 |     operator<(const multiset<_Key, _Compare, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_multiset.h:1011:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::multiset<_Key, _Compare, _Allocator>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/deque:66,
                 from /usr/include/c++/14/queue:62,
                 from a.cc:5:
/usr/include/c++/14/bits/stl_deque.h:2334:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const deque<_Tp, _Alloc>&, const deque<_Tp, _Alloc>&)'
 2334 |     operator<(const deque<_Tp, _Alloc>& __x, const deque<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:2334:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::deque<_Tp, _Alloc>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/queue:66:
/usr/include/c++/14/bits/stl_queue.h:397:5: note: candidate: 'template<class _Tp, class _Seq> bool std::operator<(const queue<_Tp, _Seq>&, const queue<_Tp, _Seq>&)'
  397 |     operator<(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_queue.h:397:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::queue<_Tp, _Seq>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/stack:63,
                 from a.cc:7:
/usr/include/c++/14/bits/stl_stack.h:373:5: note: candidate: 'template<class _Tp, class _Seq> bool std::operator<(const stack<_Tp, _Seq>&, const stack<_Tp, _Seq>&)'
  373 |     operator<(const stack<_Tp, _Seq>& __x, const stack<_Tp, _Seq>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_stack.h:373:5: note:   template argument deduction/substitution failed:
a.cc:51:28: note:   'std::basic_ostream<char>' is not derived from 'const std::stack<_Tp, _Seq>'
   51 |             else cout<<'x'<endl;
      |                            ^~~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from a.cc:8:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic