## https://yukicoder.me/problems/no/1059

class UnionFind:
    """
    UnionFindの基本的な処理を実装したクラス
    """

    def __init__(self, size):
        self.root = [i for i in range(size)]
        self.size = [1] * size

    def get_root(self, v):
        if v == self.root[v]:
            return v
        else:
            old_root = self.root[v]
            new_root = self.get_root(old_root)
            self.root[v] = new_root
            return new_root

    def merge(self, u, v):
        root_u = self.get_root(u)
        root_v = self.get_root(v)
        if root_u == root_v:
            return False

        if self.size[root_u] >= self.size[root_v]:
            self.size[root_u] += self.size[root_v]
            self.root[root_v] = root_u
            self.root[v] = root_u
        else:
            self.size[root_v] += self.size[root_u]
            self.root[root_u] = root_v
            self.root[u] = root_v
        return True
    

def main():
    L, R = map(int, input().split())

    uf = UnionFind(R + 1)

    for l in range(L, R + 1):
        x = 2 * l
        while x <= R:
            uf.merge(l, x)
            x += l

    min_composites = {}    
    for l in range(L, R + 1):
        root_l = uf.get_root(l)
        if root_l not in min_composites:
            min_composites[root_l] = l

    print(len(min_composites) - 1)
    




if __name__ == "__main__":
    main()