#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

class UnionFind {
	public:
		vector<ll> table, num;

		UnionFind(){}
		UnionFind(int size){
			table.resize(size, -1);
			num.resize(size, 1);
		}

		int find(int x){
			if (table[x] < 0) return x;
			else {
				table[x] = find(table[x]);
				return table[x];
			}
		}

		bool same(int x, int y) {
			return find(x) == find(y);
		}

		bool is_root(int x){
			if (table[x] < 0) return true;
			else return false;
		}

		ll get_size(int x){
			return num[find(x)];
		}

		void unite(int x, int y){
			int r1 = find(x);
			int r2 = find(y);
			if (r1 != r2) {
				if (table[r1] > table[r2]){
					table[r2] = r1;
					table[r1]--;
					num[r1] += num[r2];
					num[r2]--;
				} else {
					table[r1] = r2;
					table[r2]--;
					num[r2] += num[r1];
					num[r1]--;
				}
			}
			return;
		}
};

int main() {
	int l, r; cin >> l >> r;
	UnionFind uf(r-l+1);
	for (int i = l; i < r+1; ++i) {
		for (int j = 2*i; j < r+1; j += i) {
			uf.unite(i-l, j-l);
		}
	}
	int ans = -1;
	for (int i = 0; i < r-l+1; ++i) {
		if (uf.is_root(i)) ans++;
	}
	cout << ans << endl;
	return 0;
}