Im new to C++, for some reason my first sum becomes a really big negative number while that part works perfect on its own. Help

Question

#include<iostream>
using namespace std;

int main()
{
int myVariable = 10;
int b;
int c = 0;
int sum = myVariable + b + c;

cout << "10 + b = ? \nEnter a number for b: "; cin >> b;

cout << "The sum is: " << sum << endl;
if(sum>=100){
cout << "What a big number! " << sum << " !";
}
while(sum<100){
cout << "try adding a number to get a sum greater then 99" << endl;
cin >> c;
cout << "the sum is now: " << sum << endl;
return 0;
}
}

Answer 1

you must initialize a variable before using it, otherwise b is going to store some garbage

Answer 2

@sachin its not a problem, b is not initialized, so sum stores negative number(cuz b is -29348383949 smth like that)☺