c++ - lvalue required as increment operand error when using #define

Whats the problem with the code below, and why I'm getting this error?

#include 
#define A 1
using namespace std;

int main()
{
   cout <   return 0;

}

Answer

#define A 1

A is not valid c++ left value, so gave us "lvalue required as increment operand"

int A; 

is valid c++ left value and will work, also of other simple number type float, unsigned char etc