Language: C++

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i=0;i<n;++i)
#define rep1(i,n) for(int i=1;i<=n;++i)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout<< (x) << " "
int main(){
    int a,b;cin>>a>>b;
    a>=b?co("safe")*co("unsafe");
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:20: error: no match for 'operator*' (operand types are 'const char [2]' and 'std::ostream' {aka 'std::basic_ostream<char>'})
   10 |     a>=b?co("safe")*co("unsafe");
      |                    ^
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:6:15: note:   mismatched types 'const std::complex<_Tp>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   mismatched types 'const std::complex<_Tp>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'const std::complex<_Tp>'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
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:6:15: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   mismatched types 'const std::valarray<_Tp>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   mismatched types 'const std::valarray<_Tp>' and 'const char [2]'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
/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:6:15: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'const std::valarray<_Tp>'
    6 | #define co(x) cout << (x) << "\n"
      |               ^~~~
a.cc:10:21: note: in expansion of macro 'co'
   10 |     a>=b?co("safe")*co("unsafe");
      |                     ^~
a.cc:10:33: error: expected ':' before ';' token
   10 |     a>=b?co("safe")*co("unsafe");
      |                                 ^
a.cc:10:33: error: expected primary-expression before ';' token