#include <bits/stdc++.h>

typedef uint32_t u32;
typedef uint64_t u64;
typedef int32_t s32;
typedef int64_t s64;

s32 ri() {
	s32 n;
	scanf("%" SCNd32, &n);
	return n;
}
struct UnionFind {
	std::vector<int> data;
	UnionFind (int size) : data(size, -1) {}
	bool unite(int x, int y) {
		x = root(x);
		y = root(y);
		if (x != y) {
			if (data[y] < data[x]) std::swap(x, y);
			data[x] += data[y];
			data[y] = x;
		}
		return x != y;
	}
	bool same(int x, int y) { return root(x) == root(y); }
	int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
	int size(int x) { return -data[root(x)]; }
	bool connected() { return size(0) == (int) data.size(); }
};

int main() {
#define int WHOOOO // 脱int訓練中につき許して
	s32 l = ri(), r = ri();
	UnionFind uni(r + 1);
	for (s32 i = l; i <= r; i++)
		for (s32 j = i * 2; j <= r; j += i) uni.unite(i, j);
	std::set<s32> all;
	for (s32 i = l; i <= r; i++) all.insert(uni.root(i));
	printf("%" PRId32 "\n", (s32) all.size() - 1);
	return 0;
}