What is wrong in this code no test cases are passed

#1

#include
using namespace std;
int main() {
int r,sum=0; n;
cout<<"enter a number "<<endl;
cin>>n;

while(n!=0)
{
   r=n%10;
   sum=sum*10 + r;
   n=n/10;
}

cout<<sum<<endl;
return 0;

}

#2

don’t print this statment
because it is not mention in the question

your output must exactly match with given sample output

#3

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