Language: C++

#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)#include <iostream>
using namespace std;
int main(){
  int a,a2,i=1,j=1,b,b2;
  cin>>a>>b;
  while(1){
    a2=a*i;
    b2=b*j;
    if(a2==b2)break; 
    else if(a2<b2)
      i++;
    else j++;
  }  
  if(a<b){
    for(i=2;i<a+1;i++)
      if(a%i==0 && b%i==0)break;
      cout<<i<<endl;
  }
  else {
      for(i=2;i<b+1;i++)
	if(a%i==0 && b%i==0)break;
      cout<<i<<endl;
  } 

  cout<<a2<<endl; 
  return 0;
}

Compiler output:
a.cc:10:19: error: stray '#' in program
   10 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc:19:19: error: stray '#' in program
   19 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc:28:19: error: stray '#' in program
   28 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc:37:19: error: stray '#' in program
   37 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc:46:19: error: stray '#' in program
   46 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc:55:19: error: stray '#' in program
   55 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc:64:19: error: stray '#' in program
   64 |     else if(a2<b2)#include <iostream>
      |                   ^
a.cc: In function 'int main()':
a.cc:10:20: error: 'include' was not declared in this scope
   10 |     else if(a2<b2)#include <iostream>
      |                    ^~~~~~~
a.cc:10:37: error: expected primary-expression before '>' token
   10 |     else if(a2<b2)#include <iostream>
      |                                     ^
a.cc:11:1: error: expected primary-expression before 'using'
   11 | using namespace std;
      | ^~~~~
a.cc:12:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   12 | int main(){
      |         ^~
a.cc:12:9: note: remove parentheses to default-initialize a variable
   12 | int main(){
      |         ^~
      |         --
a.cc:12:9: note: or replace parentheses with braces to value-initialize a variable
a.cc:12:11: error: a function-definition is not allowed here before '{' token
   12 | int main(){
      |           ^
a.cc:90:2: error: expected '}' at end of input
   90 | }
      |  ^
a.cc:6:11: note: to match this '{'
    6 |   while(1){
      |           ^
a.cc:90:2: error: expected '}' at end of input
   90 | }
      |  ^
a.cc:3:11: note: to match this '{'
    3 | int main(){
      |           ^