#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
const int INF = 2e9 + 10;
int a, b, k;
int number_of_divisors(int number, int i) {
    if(i == number) {
        return 1;
    }
    int cost = 0;
    if(number % i == 0) {
        cost = 1;
    }
    return number_of_divisors(number, i + 1) + cost;
}
bool is_k_divible(int number, int cnt_divs, int i) {
    if(i == number) {
        return true;
    }
    bool ret = true;
    int cnt_i_divs = number_of_divisors(i, 1);
    if(cnt_i_divs >= cnt_divs) {
        return false;
    }
    ret &= is_k_divible(number, cnt_divs, i + 1);
    return ret;
}
int rec(int i) {
    if(i == b + 1) {
        return 0;
    }
    int cost = 0;
    if(is_k_divible(i, number_of_divisors(i, 1), max(i - k, 1))) {
        cost = i;
    }
    return rec(i + 1) + cost;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin >> a >> b >> k;
    cout << rec(a) << endl;
    return 0;
}