#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <cmath>

using namespace std;

int main() {
    freopen("input.txt", "r", stdin);
    long long a, b, k;
    cin >> a >> b >> k;
    long long ans = 0;
    for (long long i = a; i * i * i <= b; ++i) {
        ans += min(b,(long long) sqrt(i * i * i + k)) - max(a, (long long) (sqrt(i * i * i - k) + 0.999));
    }
    cout << ans;
    return 0;
}