What is the output of this program?#include using namespace

What is the output of this program?

#include 
    using namespace std;
    int main()
    {
        int num = 20;
        for ( ; ;)
        cout << num;
        return 0;
    }

1. 20
2. Compilation Error
3. Runtime Error
4. infinite times of printing num
5. None of these

There is not a condition in the for loop, So it will loop continuously.