import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int l = sc.nextInt();
		int r = sc.nextInt();
		sc.close();

		UnionFind uf = new UnionFind(r + 1);
		for (int i = l; i <= r; i++) {
			for (int j = 2; i * j <= r; j++) {
				uf.union(i, i * j);
			}
		}
		System.out.println(uf.num - l - 1);
	}

	static class UnionFind {
		int[] parent, size;
		int num = 0; // 連結成分の数

		UnionFind(int n) {
			parent = new int[n];
			size = new int[n];
			num = n;
			for (int i = 0; i < n; i++) {
				parent[i] = i;
				size[i] = 1;
			}
		}

		void union(int x, int y) {
			int px = find(x);
			int py = find(y);
			if (px != py) {
				parent[px] = py;
				size[py] += size[px];
				num--;
			}
		}

		int find(int x) {
			if (parent[x] == x) {
				return x;
			}
			parent[x] = find(parent[x]);
			return parent[x];
		}

		/**
		 * xとyが同一連結成分か
		 */
		boolean same(int x, int y) {
			return find(x) == find(y);
		}

		/**
		 * xを含む連結成分のサイズ
		 */
		int size(int x) {
			return size[find(x)];
		}
	}
}