Language: C++

#include<bits/stdc++.h>
using namespace std;
int main()
{
char a[100], b[100], c[100];
int i, j, m,n,t;
getline(cin,a);
getline(cin,b);
m=strlen(a);
n=strlen(b);
if(m=n)
t=2n;
else
t=m+n;
for(i=0;i<t;i++)
{ 
if((i+1)%2==0)
 c[i]=a[i];
else
c[i]=b[i];
}
c[t]='\0';
return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:8: error: no matching function for call to 'getline(std::istream&, char [100])'
    7 | getline(cin,a);
      | ~~~~~~~^~~~~~~
In file included from /usr/include/c++/14/string:55,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.tcc:907:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
  907 |     getline(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:907:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/string:54:
/usr/include/c++/14/bits/basic_string.h:4117:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 4117 |     getline(basic_istream<_CharT, _Traits>& __is,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4117:5: note:   template argument deduction/substitution failed:
a.cc:7:8: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'char [100]'
    7 | getline(cin,a);
      | ~~~~~~~^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4125:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 4125 |     getline(basic_istream<_CharT, _Traits>&& __is,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4125:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/basic_string.h:4132:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 4132 |     getline(basic_istream<_CharT, _Traits>&& __is,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4132:5: note:   template argument deduction/substitution failed:
a.cc:7:8: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'char [100]'
    7 | getline(cin,a);
      | ~~~~~~~^~~~~~~
In file included from /usr/include/c++/14/cstdio:42,
                 from /usr/include/c++/14/ext/string_conversions.h:45,
                 from /usr/include/c++/14/bits/basic_string.h:4154:
/usr/include/stdio.h:697:18: note: candidate: '__ssize_t getline(char**, size_t*, FILE*)'
  697 | extern __ssize_t getline (char **__restrict __lineptr,
      |                  ^~~~~~~
/usr/include/stdio.h:697:18: note:   candidate expects 3 arguments, 2 provided
a.cc:8:8: error: no matching function for call to 'getline(std::istream&, char [100])'
    8 | getline(cin,b);
      | ~~~~~~~^~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:907:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
  907 |     getline(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:907:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/basic_string.h:4117:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 4117 |     getline(basic_istream<_CharT, _Traits>& __is,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4117:5: note:   template argument deduction/substitution failed:
a.cc:8:8: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'char [100]'
    8 | getline(cin,b);
      | ~~~~~~~^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4125:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 4125 |     getline(basic_istream<_CharT, _Traits>&& __is,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4125:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/basic_string.h:4132:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::getline(basic_istream<_CharT, _Traits>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 4132 |     getline(basic_istream<_CharT, _Traits>&& __is,
      |     ^~~~~~~
/usr/include/c++/14/bits/basic_string.h:4132:5: note:   template argument deduction/substitution failed:
a.cc:8:8: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'char [100]'
    8 | getline(cin,b);
      | ~~~~~~~^~~~~~~
/usr/include/stdio.h:697:18: note: candidate: '__ssize_t getline(char**, size_t*, FILE*)'
  697 | extern __ssize_t getline (char **__restrict __lineptr,
      |                  ^~~~~~~
/usr/include/stdio.h:697:18: note:   candidate expects 3 arguments, 2 provided
a.cc:12:3: error: unable to find numeric literal operator 'operator""n'
   12 | t=2n;
      |   ^~