#include <iostream>
#include <cstring>
#include <cmath>
#include <math.h>
#include <vector>
#include <queue>
using namespace std;

int num_of_divisors_of_x(int x, int i) {
    if(i > x) {
        return 0;
    }
    int divisor = 0;
    if(x % i == 0) {
        divisor = 1;
    }
    return num_of_divisors_of_x(x, i + 1) + divisor;
}

int k_deliv(int A, int B) {
    if(A > B) {
        return 0;
    }
    return max(num_of_divisors_of_x(A, 1), k_deliv(A + 1, B));
}
// k_deliv(17, 23) = max(2, k_deliv(18, 23)) = max(2, 6) = 6
// k_deliv(18, 23) = max(6, k_deliv(19, 23)) = max(6, 6) = 6
// k_deliv(19, 23) = max(2, k_deliv(20, 23)) = max(2, 6) = 6
// k_deliv(20, 23) = max(6, k_deliv(21, 23)) = max(6, 4) = 6
// k_deliv(21, 23) = max(4, k_deliv(22, 23)) = max(4, 4) = 4
// k_deliv(22, 23) = max(4, k_deliv(23, 23)) = max(4, 2) = 4
// k_deliv(23, 23) = max(2, k_deliv(24, 23)) = max(2, 0) = 2
// k_deliv(24, 23) = 0
int sum(int A, int B, int K) {
    if(A > B) {
        return 0;
    }
    int div_A = num_of_divisors_of_x(A, 1);
    int div_K = k_deliv(max(1, A - K), A - 1);
    int suma = 0;
    if(div_A > div_K) {
        suma = A;
    }
    return sum(A + 1, B, K) + suma;
}
// div_A = 8
// k_deliv(17, 23) = 6
int main()
{
    int A, B, K;
    cin >> A >> B >> K;
    cout << sum(A, B, K) << endl;
    
    
    // 24
    
    
    return 0;
}