[C++][3] Variables

#include <iostream> //pre-processor directive

using namespace std; //std library

int main() //it starts with the main 1st
{
    int a = 4; //variable a
    int b = 21; //variable b

    int sum = a + b; //summation
    int diff = a - b; // subtraction/difference

    cout << sum << endl;
    cout << diff;

    return 0; //to tell that program ran fine
}