// AOJ 2275: Fox Number
// 2017.12.11 bal4u@uu

#include <stdio.h>
#include <string.h>
#include <math.h>

#define MAX  1000005			// sqrt(1e12)
char tbl[MAX+1];

int sz;						// max sz = 78500, prime[0] = 2, prime[78499] = 1000005
int prime[79000] = {  		// prime[168] = 1009, prime[169] = 1013, 1009^2 = 1018081
  2, 3,  5,  7, 11, 13, 17, 19, 23, 29, 
 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 
 73, 79, 83, 89, 97,101,103,107,109,113, 
127,131,137,139,149,151,157,163,167,173,
179,181,191,193,197,199,211,223,227,229, 
233,239,241,251,257,263,269,271,277,281, 
283,293,307,311,313,317,331,337,347,349, 
353,359,367,373,379,383,389,397,401,409, 
419,421,431,433,439,443,449,457,461,463, 
467,479,487,491,499,503,509,521,523,541, 
547,557,563,569,571,577,587,593,599,601, 
607,613,617,619,631,641,643,647,653,659, 
661,673,677,683,691,701,709,719,727,733, 
739,743,751,757,761,769,773,787,797,809, 
811,821,823,827,829,839,853,857,859,863, 
877,881,883,887,907,911,919,929,937,941, 
947,953,967,971,977,983,991,997,1009 };

int sqp[169] = {				// squre of prime: sqp[i] = prime[i] * prime[i]
  4, 9,25,49,121,169,289,361,529,841,961,
1369,1681,1849,2209,2809,3481,3721,4489,5041,
5329,6241,6889,7921,9409,10201,10609,11449,11881,12769,
16129,17161,18769,19321,22201,22801,24649,26569,27889,29929,
32041,32761,36481,37249,38809,39601,44521,49729,51529,52441,54289,
57121,58081,63001,66049,69169,72361,73441,76729,78961,80089,85849,
94249,96721,97969,100489,109561,113569,120409,121801,124609,128881,
134689,139129,143641,146689,151321,157609,160801,167281,175561,177241,
185761,187489,192721,196249,201601,208849,212521,214369,218089,229441,
237169,241081,249001,253009,259081,271441,273529,292681,299209,310249,
316969,323761,326041,332929,344569,351649,358801,361201,368449,375769,
380689,383161,398161,410881,413449,418609,426409,434281,436921,452929,
458329,466489,477481,491401,502681,516961,528529,537289,546121,552049,
564001,573049,579121,591361,597529,619369,635209,654481,657721,674041,
677329,683929,687241,703921,727609,734449,737881,744769,769129,776161,
779689,786769,822649,829921,844561,863041,877969,885481,896809,908209,
935089,942841,954529,966289,982081,994009,1018081 };

void sieve()
{
	int i, j, k;

	for (i = 1; i < 169; i++) {
		k = prime[i];
		for (j = sqp[i]; j < MAX; j += k) tbl[j] = 1;
	}
	for (sz = 168, i = 1009; i <= MAX; i += 2) if (!tbl[i]) prime[sz++] = i;
}

int base[1000002];
int idx [1000002];

int bsch(int x)
{
	int m, l = 0, r = sz;

    while (l < r) {
        m = (l + r) >> 1;
		if (prime[m] == x) return m;
        if (prime[m] < x) l = m + 1; else r = m;
    }
	return l-1;
}

int main()
{
	int i, k, p0, ans;
	long long A, B, a, b, j, pp, ll, rr, t;

	sieve();

	scanf("%lld%lld", &A, &B);
	a = A-B, b = A+B;
	if (b <= 1) { puts("0"); return 0; }
	if (a <= 1) a = 2;

	sz = bsch((int)sqrt((double)b));

	memset(idx, 1, sizeof(idx));
	for (i = 0; i <= sz; i++) {
		p0 = prime[i];
		for (k = 0, j = p0; j <= b; j *= p0, k++);
		for (j /= p0; j > 1; j /= p0, k--) {
			pp = j, ll = pp*(1+(a-1)/pp), rr = pp*(b/pp);
			for (t = ll-a; ll <= rr; ll += pp, t += pp) {
				if (!idx[t] || base[t] == p0) continue;
				if (idx[t] < k) idx[t] = 0;
				else base[t] = p0, idx[t] = k;
			}
		}
	}

	ans = 0, i = (int)(b-a+1); while (i--) if (idx[i]) ans++;
	printf("%d\n", ans);
	return 0;
}

Measured memory_bytes: 10816