#include <stdio.h>

#define min(a, b) ((a) < (b) ? (a) : (b))
#define REP(i, n) for ((i) = 0; i < (n); ++i)
#define MAX 50000
#define LIMIT 7000

bool isP[MAX];
int primes[LIMIT], a, b, k;
void sieve() {
    int i, k = 0, j;
    isP[0] = isP[1] = 1;
    for (i = 2; i * i < MAX; ++i) {
        if (!isP[i]) {
            for (j = i * i; j < MAX; j += i) {
                isP[j] = 1;
            }
        }
    }
    REP (i, MAX) {
        if (!isP[i] && k < LIMIT) {
            primes[k++] = i;
        }
    }
}
bool isPrime(int n) {
    if (MAX > n) {
        return !isP[n];
    } else {
        int i;
        for (i = 0; i < LIMIT && primes[i] != 0; ++i) {
            if (n % primes[i] == 0) {
                return 0;
            }
        }
        return 1;
    }
}
int f(int n, int i) {
    if (n < 1) {
        return 0;
    }
    int j;
    int res = n;
    for (j = i; primes[j] < k && primes[j] <= n; ++j) {
        res -= f(n / primes[j], j + 1);
    }
    return res;
}
int main() {
    sieve();
    scanf("%d %d %d", &a, &b, &k);
    if (!isPrime(k)) {
        puts("0");
    } else {
        printf("%d\n", f(b / k, 0) - f((a - 1) / k, 0));
    }
    return 0;
}