public class Main { public static void main(String[] args) { new Main(); } public Main() { FastScanner fs = new FastScanner(); java.io.PrintWriter out = new java.io.PrintWriter(System.out); solve(fs, out); out.flush(); //if (fs.hasNext()) throw new AssertionError("read input"); } public void solve(FastScanner fs, java.io.PrintWriter out) { int A = fs.nextInt(), B = fs.nextInt(); if (B == 0) out.println(1); else if (A == -1) out.println(2); else out.println(-1); } static class FastScanner { private final java.io.InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) return true; ptr = 0; try { buflen = in.read(buffer); } catch (java.io.IOException e) { e.printStackTrace(); } return buflen > 0; } private byte readByte() { return hasNextByte() ? buffer[ptr++ ] : -1; } private static boolean isPrintableChar(byte c) { return 32 < c || c < 0; } private static boolean isNumber(int c) { return '0' <= c && c <= '9'; } public boolean hasNext() { while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++ ; return hasNextByte(); } public String next() { if (!hasNext()) throw new java.util.NoSuchElementException(); StringBuilder sb = new StringBuilder(); byte b; while (isPrintableChar(b = readByte())) sb.appendCodePoint(b); return sb.toString(); } public final long nextLong() { if (!hasNext()) throw new java.util.NoSuchElementException(); long n = 0; try { byte b = readByte(); if (b == '-') { while(isNumber(b = readByte())) n = n * 10 + '0' - b; return n; } else if (!isNumber(b)) throw new NumberFormatException(); do n = n * 10 + b - '0'; while (isNumber(b = readByte())); } catch (java.util.NoSuchElementException e) { } return n; } public final int nextInt() { if (!hasNext()) throw new java.util.NoSuchElementException(); int n = 0; try { byte b = readByte(); if (b == '-') { while(isNumber(b = readByte())) n = n * 10 + '0' - b; return n; } else if (!isNumber(b)) throw new NumberFormatException(); do n = n * 10 + b - '0'; while (isNumber(b = readByte())); } catch (java.util.NoSuchElementException e) { } return n; } public double nextDouble() { return Double.parseDouble(next()); } } public static class Arrays { public static void sort(final int[] array) { int l, min = 0xFFFFFFFF, max = 0; for (l = 0;l < array.length;++ l) { int i = array[l]; min &= i; max |= i; if ((i & 0x80000000) == 0) break; } for (int r = l + 1;r < array.length;++ r) { int i = array[r]; min &= i; max |= i; if ((i & 0x80000000) != 0) { array[r] = array[l]; array[l ++] = i; } } int use = min ^ max, bit = Integer.highestOneBit(use & 0x7FFFFFFF); if (bit == 0) return; sort(array, 0, l, use, bit); sort(array, l, array.length, use, bit); } private static void sort(final int[] array, final int left, final int right, final int use, int digit) { if (right - left <= 96) { for (int i = left + 1;i < right;++ i) { int tmp = array[i], tmp2, j; for (j = i;j > left && (tmp2 = array[j - 1]) > tmp;-- j) array[j] = tmp2; array[j] = tmp; } return; } int l = left; while(l < right && (array[l] & digit) == 0) ++ l; for (int r = l + 1;r < right;++ r) { int i = array[r]; if ((i & digit) == 0) { array[r] = array[l]; array[l ++] = i; } } if ((digit = Integer.highestOneBit(use & digit - 1)) == 0) return; sort(array, left, l, use, digit); sort(array, l, right, use, digit); } public static void sort(final long[] array) { int l; long min = 0xFFFFFFFFFFFFFFFFL, max = 0; for (l = 0;l < array.length;++ l) { long i = array[l]; min &= i; max |= i; if ((i & 0x8000000000000000L) == 0) break; } for (int r = l + 1;r < array.length;++ r) { long i = array[r]; min &= i; max |= i; if ((i & 0x8000000000000000L) != 0) { array[r] = array[l]; array[l ++] = i; } } long use = min ^ max, bit = Long.highestOneBit(use & 0x7FFFFFFFFFFFFFFFL); if (bit == 0) return; sort(array, 0, l, use, bit); sort(array, l, array.length, use, bit); } private static void sort(final long[] array, final int left, final int right, final long use, long digit) { if (right - left <= 96) { for (int i = left + 1, j;i < right;++ i) { long tmp = array[i], tmp2; for (j = i;j > left && (tmp2 = array[j - 1]) > tmp;-- j) array[j] = tmp2; array[j] = tmp; } return; } int l = left; while(l < right && (array[l] & digit) == 0) ++ l; for (int r = l + 1;r < right;++ r) { long i = array[r]; if ((i & digit) == 0) { array[r] = array[l]; array[l ++] = i; } } if ((digit = Long.highestOneBit(use & digit - 1)) == 0) return; sort(array, left, l, use, digit); sort(array, l, right, use, digit); } } public static class IntMath { public static int gcd(int a, int b) { while (a != 0) if ((b %= a) != 0) a %= b; else return a; return b; } public static int gcd(int... array) { int ret = array[0]; for (int i = 1;i < array.length;++ i) ret = gcd(ret, array[i]); return ret; } public static long gcd(long a, long b) { while (a != 0) if ((b %= a) != 0) a %= b; else return a; return b; } public static long gcd(long... array) { long ret = array[0]; for (int i = 1;i < array.length;++ i) ret = gcd(ret, array[i]); return ret; } public static long lcm(long a, long b) { return a / gcd(a, b) * b; } public static int pow(int a, int b) { int ans = 1; for (int mul = a;b > 0;b >>= 1, mul *= mul) if ((b & 1) != 0) ans *= mul; return ans; } public static int pow(int a, int b, int mod) { if (b < 0) b = b % (mod - 1) + mod - 1; long ans = 1; for (long mul = a;b > 0;b >>= 1, mul = mul * mul % mod) if ((b & 1) != 0) ans = ans * mul % mod; return (int)ans; } public static int floorsqrt(long n) { return (int)Math.sqrt(n + 0.1); } public static int ceilsqrt(long n) { return n <= 1 ? (int)n : (int)Math.sqrt(n - 0.1) + 1; } } }