Function in hailstone sequence to find longest sequence and another to find the starting number

So there are two function that I don't know how to write for this program. The first one would take an integer n and return the length of the longest hailstone longest hailstone sequence starting at a number from 1 to n.

The second function I don't know how to write is meant to take an integer n and return the start value of the longest hailstone sequence that starts on a value from 1 to n. How do I go about writing these? here is my code so far.

#include <cstdio>
using namespace std;

// The function next(n)takes an integer value n and 
// returns the number that follows n in a hailstone sequence. 
// For example: next(7) = 22 and next(22) = 11.

int next(int n)
{
       if (n == 1)
    {
    return n;
    }
       else if (n%2==0)
    {
    return n=n/2;
    }
       else
    {
    return n=3*n+1;
   }
}

// The function hailstone reads int n and 
// prints its entire hailstone sequence.
// Parameters: int n. Uses next() function.

void sequence(int n)
{
  printf("%i ",n);
  if(n!=1)
    {
      n=next(n);
      sequence(n);
    }
} 

// Parameters: int length, int n
// Uses next function, to calculate the length of the sequence.

int length(int n) 
{
  int length = 1;
  while (n > 1)
    {
      n = next(n);
      ++length;
    }
  return length;
}

int largest(int n)
{
  if(n==1)
  {
    return 1;
  }
  int maxint = largest(next(n));
  return maxint>n? maxint:n;
}

int main()
{
  int n; 

  printf("What number shall I start with? ");
  scanf("%i", &n);

  printf("The hailstone sequence starting at %i is:", n);
  sequence(n);

  printf("\nThe length of the sequence is: %i", length(n));

  printf("\nThe largest number in the sequence is: %i", largest(n));

  printf("\nThe longest hailstone sequence starting with a number ");
  printf("up to %i has length %i",n, length(n));

  printf("\nThe longest hailstone sequence starting with a number ");
  printf("up to %i begins with %i\n",n,n);

  return 0;
}