Why does my code take integer 8 as default when no number in entered through cin.

Question

This is happening in code playground. So pls check the code there and here is code :-

#include <iostream>
using namespace std;
int main(){
int x, y, z;
/* For single input */
cin >> x;
cout << "Enter a number: " << x << endl;
/* For multiple inputs*/
cout << "Enter 2 numbers: ";
cin >> y >> z;
cout << "Sum = " << (x+y+z);
return 0;
}