C :

#include<stdio.h>
#include<string.h>
int main()
{
    int x,s=0;

    while(scanf("%d",&x),x)
    {

        for(s=0;x>1;)
        {
            if(x%2==0)
            {
                x=x/2;
                s++;

            }else
            {
                x=3*x+1;
                x=x/2;
                s++;
            }
        }
        printf("%d\n",s);
    }
}

C++ :

#include <cstdio>

int cal(int x) {
    if (1 == x)
        return 0;
    if (x & 1) x = x * 3 + 1;
    return cal(x / 2) + 1;
}

int main() {
    //freopen("data.in", "r", stdin);
    //freopen("data.out", "w", stdout);
    int n;
    while (EOF != scanf("%d", &n)) {
        if (0 == n)
            break;
        printf("%d\n", cal(n));
    }
    return 0;
}

Java :

import java.util.Scanner;
public class Main{
  public static void main(String[] args){
    int n, i;
    Scanner in=new Scanner(System.in);
    while(in.hasNextInt()){
      n = in.nextInt();
      if(n == 0)
        System.exit(0);
      for(i = 0; n != 1; i++){
        if(n % 2 == 0)
          n /= 2;
        else
          n = (3 * n + 1) / 2;
      }
      System.out.println(i);
    }
  }
}