Language: C++

#include<iostream>
#include<stdio.h>
#include <algorithm>
#include<string.h>
#include <utility>
using namespace std;
using namespace std;
int main(){
	int m;
	string in[90],in2[90];
	int a[90],b[90],ans[90];
	int f;
	int a_len,b_len,m_len;
	cin>>m;
	while(m--){
		for(int i=0;i<90;i++){
			a[i]=b[i]=ans[i]=0;
		}
		cin>>in;
		cin>>in2;
		a_len=in.size();
		b_len=in2.size();
		for(int i=0;i<a_len;i++){
			a[a_len-1-i]=in[i]-'0';
		}
		for(int i=0;i<b_len;i++){
			b[b_len-1-i]=in[i]-'0';
		}
		m_len=max(a_len,b_len);
		/*
		if(m_len>80){
			cout<<"overflow"<<endl;
			continue;
		}
		f=0;
		for(int i=0;i<m_len+1;i++){
			ans[i]=(a[i]+b[i]+f)%10;
			f=(a[i]+b[i]+f)/10;
		}
		if(ans[m_len]!=0){
			if(m_len>79){
				cout<<"overflow"<<endl;
				continue;
			}
			cout<<ans[m_len];
		}
		for(int i=0;i<m_len;i++){
			cout<<ans[m_len-1-i];
		}cout<<endl;
		
		*/
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:19:20: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'std::string [90]' {aka 'std::__cxx11::basic_string<char> [90]'})
   19 |                 cin>>in;
      |                 ~~~^~~~
      |                 |    |
      |                 |    std::string [90] {aka std::__cxx11::basic_string<char> [90]}
      |                 std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'std::string*' {aka 'std::__cxx11::basic_string<char>*'}
   19 |                 cin>>in;
      |                      ^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'short int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(short int)((std::string*)(& in))' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'short unsigned int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(short unsigned int)((std::string*)(& in))' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(int)((std::string*)(& in))' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'unsigned int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(unsigned int)((std::string*)(& in))' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(long int)((std::string*)(& in))' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long unsigned int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(long unsigned int)((std::string*)(& in))' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long long int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(long long int)((std::string*)(& in))' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long long unsigned int' [-fpermissive]
   19 |                 cin>>in;
      |                      ^~
      |                      |
      |                      std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:19:22: error: cannot bind rvalue '(long long unsigned int)((std::string*)(& in))' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:19:22: error: cannot bind non-const lvalue reference of type 'void*&' to an rvalue of type 'void*'
   19 |                 cin>>in;
      |                      ^~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:25: note:   no known conversion for argument 1 from 'std::string [90]' {aka 'std::__cxx11::basic_string<char> [90]'} to 'float&'
  219 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:26: note:   no known conversion for argument 1 from 'std::string [90]' {aka 'std::__cxx11::basic_string<char> [90]'} to 'double&'
  223 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:31: note:   no known conversion for argument 1 from 'std::string [90]' {aka 'std::__cxx11::basic_string<char> [90]'} to 'long double&'
  227 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_i