// OK B region first tour 17/18

# include <iostream>
# include <cmath>

using namespace std;

int64_t check(double x) {
    double const EPS = 0.0000001;
    if (abs(ceil(x) - x) <= EPS) {
        return ceil(x);
    } else {
        return floor(x);
    }
}

int main() {
    int64_t a, b, k;
    cin >> a;
    cin >> b;
    cin >> k;
    int64_t res = 0;
    auto example = static_cast<int64_t> (check(pow(b, 1 / 3.0)));
    for (size_t i = static_cast<int64_t> (ceil(pow(a, 1 / 3.0))); i <= static_cast<int64_t> (check(pow(b, 1 / 3.0))); i++) {
        int64_t left = max(static_cast<int64_t> (ceil(pow(max(pow(i, 3) - k, 1.0), 1 / 2.0))), static_cast<int64_t> (ceil(pow(a, 1 / 2.0))));
        int64_t right = min(static_cast<int64_t> (check(pow(pow(i, 3) + k, 1 / 2.0))), static_cast<int64_t> (check(pow(b, 1 / 2.0))));
        res += max(right - left + 1, static_cast<int64_t> (0));
    }
    cout << res;
    return 0;
}