C++ Function Exercise - Keeps returning zero

Total beginner.

The exercise is to make a function that takes an input and if the input is even, a certain calculation is done. If odd, a calculation is done. Then the new value is reassigned and the sequence continues until 1 is reached.

Example: If the starting integer is 1, the return value should be 0, since it takes no steps to reach one. If the starting integer is 3, then the sequence would go: 3, 10, 5, 16, 8, 4, 2, 1, and the return value should be 7.

Been messing with this for hours and I keep getting a return of 0 from counter.

(The main() is used only for testing purposes)

Thanks

#include <iostream>

using namespace std;

int hailstone(int outinput);

int main()
{
  int outinput=10, counter;

  hailstone(outinput);

  cout << counter << endl;

  return 0;
}

int hailstone(int outinput)
{
  int counter;

  for(outinput; outinput == 1; )
  {
    if(outinput % 2 == 0)
    {
      outinput = outinput / 2;
      counter++;
    }
    else if(outinput % 2 != 0)
    {
      outinput = outinput * 3 + 1;
      counter++;
    }
  }

  return counter;
}