找规律 SGU 126 Boxes

题目地址：http://acm.sgu.ru/problem.php?contest=0&problem=126

/*
    找规律，智商不够，看了题解
    详细解释：http://blog.csdn.net/ahfywff/article/details/7432524
*/
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <iostream>
#include <algorithm>
#include <queue>
#include <vector>
using namespace std;

const int MAXN = 1e5 + 10;
const int INF = 0x3f3f3f3f;

int GCD(int a, int b)
{
    return b ? GCD (b, a % b) : a;
}

int main(void)        //SGU 126 Boxes
{
    //freopen ("C.in", "r", stdin);

    int n, m;

    while (~scanf ("%d%d", &n, &m))
    {
        int ans;
        if (n == 0 || m == 0)
        {
            ans = 0;
        }
        else
        {
            if (n < m)  swap (n, m);
            int k = GCD (n, m);
            int x = n / k;  int y = m / k;
            if ((x+y) & 1)
            {
                ans = -1;
            }
            else
            {
                int tmp = x + y;
                ans = 0;
                while (tmp > 1)
                {
                    if (tmp % 2 == 0)
                    {
                        tmp /= 2;
                        ans++;
                    }
                    else
                    {
                        ans = -1;    break;
                    }
                }
            }
        }

        printf ("%d
", ans);
    }

    return 0;
}