/* -*- coding: utf-8 -*-
 *
 * 982.cc:  No.982 Add - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_A = 100;
const int MAX_B = 100;
const int MAX_N = MAX_A * MAX_A + MAX_B * MAX_B;

/* typedef */

/* global variables */

bool used[MAX_N + 1];

/* subroutines */

template <typename T>
T gcd(T m, T n) {  // m > 0, n > 0
  if (m < n) swap(m, n);
  while (n > 0) {
    T r = m % n;
    m = n;
    n = r;
  }
  return m;
}

/* main */

int main() {
  int a, b;
  scanf("%d%d", &a, &b);

  if (gcd<int>(a, b) > 1) {
    puts("-1");
    return 0;
  }
  
  int maxn = a * a + b * b;
  for (int x = 0; x <= a; x++)
    for (int y = 0, n; (n = a * x + b * y) <= maxn; y++)
      used[n] = true;

  int cnt = 0;
  for (int n = 0; n <= maxn; n++)
    if (! used[n]) cnt++;

  printf("%d\n", cnt);
  return 0;
}