#include <iostream>
#include <vector>
#include <queue>
using namespace std;

int number_of_divisors(int n, int i = 1) {
    if(i == n) {
        return 1;
    }
    int is_divisor = 0;
    if(n % i == 0) {
        is_divisor = 1;
    }
    return number_of_divisors(n, i + 1) + is_divisor;
}
int is_k(int n, int k, int N) {
    if(n == 0) {
        return 1;
    }
    if(k == 0) {
        return 1;
    }
    if(number_of_divisors(N) <= number_of_divisors(n)) {
        return 0;
    }
    return is_k(n - 1, k - 1, N);

}
int sum(int a, int b, int k) {
    if(a > b) {
        return 0;
    }
    int number = 0;
    if(is_k(a - 1, k, a)) {
        number = a;
    }
    return sum(a + 1, b, k) + number;
}
int main() {

    int a, b;
    cin >> a >> b;

    int k;
    cin >> k;
    cout << sum(a, b, k) << endl;


    return 0;
}