"0" appearing after function is completed in C++

// This program is able take two variables`
// and apply Auto increment or decrement`
// based on the user's input and by calling a function

#include <iostream>

using namespace std;

int inc (int, int); // Increment function prototype
int dec (int, int); // Decrement function prototype

int main () 
{
    int num1, num2;
    char operation = ' ', I, D;

    cout << "Enter the first variable: ";
    cin >> num1;
    cout << "Enter the second variable: ";
    cin >> num2;
    cout << endl;
    
    cout << "Do you want Auto increment, decrement or both? (Type 'I', 'D' or 'B'): ";
    cin >> operation;
    
    if (operation == 'I') {
        cout << inc(num1,num2);
    }
    else if (operation == 'D') {
        cout << dec(num1,num2);
    }
    else if (operation == 'B') {
        cout << inc(num1,num2);
        cout << endl;
        cout << dec(num1,num2);
    }
    else {
        cout << "Error please enter 'I', 'D' or 'B' as a option" << endl;
    }

    return 0;   
}

int inc (int num1, int num2) {
    num1++; num2++;
    
    cout << "Number 1 ++ is: " << num1 << endl;
    cout << "Number 2 ++ is: " << num2 << endl;
    
    return 0;
}

int dec (int num1, int num2) {
    --num1; --num2;
    
    cout << "Number 1 -- is: " << num1 << endl;
    cout << "Number 2 -- is: " << num2 << endl;
    
    return 0;
}

I just started taking Fundamentals of programming I at college and i have this assignment and this 0 keeps appearing after the function has completed

>Solution :

This happens because your inc and dec print stuff, but also return an int. You then proceed to print the return value, on these lines:

cout << inc(num1,num2);

and

cout << dec(num1,num2);

.

You can safely remove these cout << prefixes, and probably the entire return value, as it does not seem necessary to output your resuls (that happens in inc and dec).