c++ if-statement with int's

#include <iostream>

using namespace std;

int main(){
    int num1;
    int num2;
    int sum;

    cout << "Pick a number:\n";
    cin >> num1;

    cout << "Substract number " << num1 << " with:\n";
    cin >> num2;

    sum = num1 - num2;

    cout << num1 << " - " << num2 << " = " << sum << endl;

    if(sum > 50){
        cout << "Your number was larger than 50.\n";
    } else if(sum > 20){
        cout << "Your number was larger than 20.\n";
    } else if(sum < 20){
        cout << "Your number was below 20.\n";
    } else if(sum < 0){
        cout << "Cool! Your number was below 0.\n";
        // --- does not work, output will be: "Your number was below 20.".
    } else {
        cout << "Let me guess, your number was exactly 20? ;)\n";
    }

    return 0;
}