C++ compilation error in linux unqualified-id before

I am very new to C++ programming and anytime I try to compile even a very simple program this error appears. even for something as simple as

#include <iostream>

using namespace std;

int main() 
{ 

    cout << "Hello World!";

    return 0;
}

This is the error that appears. I use Vi as the linux editor.

http://i.stack.imgur.com/0pVIH.png