#include <cstdio>
#include <iostream>
#include <vector>

using namespace std;

constexpr int N = 114514;

int a;
int b;
int p;
bool judge[N];
int dad[N];
int rk[N];
int flag[N];
int res;

int find (int now) {
	return ((now == dad[now]) ? now : dad[now] = find (dad[now]));
}

void merge (int one, int two) {
	one = find (one);
	two = find (two);

	if (one == two) {
		return;
	}

	if (rk[one] > rk[two]) {
		dad[two] = one;
		rk[one] += rk[two];
	}
	else {
		dad[one] = two;
		rk[two] += rk[one];
	}
}

int main () {
	
	freopen ("setb.in", "r", stdin);
	freopen ("setb.out", "w", stdout);

	cin >> a >> b >> p;
	for (int i = 1; i <= b; i++) {
		dad[i] = i;
		rk[i] = 1;
	}

	for (int i = 2; i <= b; i++) {
		if (!judge[i]) {
			for (int j = 2; i * j <= b; j++) {
				judge[i * j] = true;
				if (i >= p) {
					merge (i * j, i);
				}
			}
		}
	}

	for (int i = a; i <= b; i++) {
		int t = find (i);
		res += !flag[t];
		flag[t] = true;
	}

	cout << res << endl;
	
	return 0;
}