Go: // AOJ Collatz's Problem :http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0158

package main

import (
	"fmt"
)

func main() {
	for {
		var n int

		fmt.Scanf("%d", &n)

		if n == 0 {
			break
		}

		count := 0
		for n != 1 {
			if n%2 == 0 {
				n /= 2
			} else {
				n = n*3 + 1
			}
			count++
		}
		fmt.Println(count)
	}
}

C++: #include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(){

	int n;
	while(cin>>n&&n!=0){
		int cnt=0;
		while(n!=1){
			if(n%2==0)
				n/=2;
			else
				n=n*3+1;
			cnt++;
		}
		cout<<cnt<<endl;
	}

	return 0;
}

C++: #include <functional>
#include <algorithm>
#include <iostream>
#include <numeric>
#include <iomanip>
#include <utility>
#include <cstdlib>
#include <sstream>
#include <bitset>
#include <vector>
#include <cstdio>
#include <ctime>
#include <queue>
#include <deque>
#include <cmath>
#include <stack>
#include <list>
#include <map>
#include <set>

using namespace std;

typedef vector<int> VI;
typedef pair<int,int> PII;
typedef long long ll;

#define dump(x)  cerr << #x << " = " << (x) << endl
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(a)  (a).begin(),(a).end()
#define PB push_back
#define sz size()

const double EPS = 1e-10;
const int INF = 100000000;

int main(){
    int n;
    while(cin>>n){
        int count=0;
        if(n==0)break;
        while(n!=1){
            if(n%2==0)n/=2;
            else n=3*n+1;
            count++;
        }
        cout<<count<<endl;
    }
    return 0;
}

C++: #include<iostream>

using namespace std;

int main(){
	 
	long long n;
	
	while( cin >> n ) {
		
	int count = 0;
	if( n == 0)
	break;
	
	while(true) {
		
		if( n == 1)
		break;
		
		else if ( n % 2)
		n = n * 3 + 1;
		
		else
		n /= 2;
		
		count++;
	}
	cout << count << "\n";
}
  	return 0;
}

C++: // clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
// #define main int main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define stlice(from, to) substr(from, (to) - (from) + 1)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
using pii = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vb = vector<bool>;
using vs = vector<string>;
using vpii = vector<pii>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvpii = vector<vpii>;
template<typename A> using fn = function<A>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
constexpr bool odd(const int &n) { return n & 1; }
constexpr bool even(const int &n) { return !odd(n); }
void solve();
main { solve(); return 0; }
// clang-format on

void solve() {
  int n;
  while (cin >> n, n) {
    int c = 0;
    while (n != 1) {
      n = even(n) ? n / 2 : n * 3 + 1;
      c++;
    }
    cout << c << endl;
  }
}

C++: #include <cstdio>
using namespace std;
int main(){
	while(1){
		int n,a=0;
		scanf("%d",&n);
		if(!n)break;
		while(n!=1){
			if(n&1)n=n*3+1;
			else n/=2;
			a++;
		}
		printf("%d\n",a);
	}
	return 0;
}

C++: 
//http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0158

#include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#include<cmath>
#include<climits>
#include<ctime>
#include<cstring>
#include<numeric>

#define ALL(v) (v).begin(),(v).end()
#define REP(i,p,n) for(int i=p;i<(int)(n);++i)
#define rep(i,n) REP(i,0,n)
#define dump(a) (cerr << #a << "=" << (a) << endl)
#define DUMP(list) cout << "{ "; for(auto nth : list){ cout << nth << " "; } cout << "}" << endl;

using namespace std;

int calc(int n){
	return (n % 2 == 0) ? n/2 : 3*n+1 ;
}

int main()
{
	int N;

	while(cin >> N && N)
	{
		int tmp=N, cnt=0;

		while(true)
		{
			cnt++;
			tmp = calc(tmp);
			if(tmp == 1){ break; }
		}

		cout << cnt << endl;
	}

	return 0;
}