include <bits/stdc++.h>

using namespace std; bool sushu(int num);

int main() {

int a, b, d, sum = 0;
cin >> a >> b >> d;
string s = " ";
for (int i = a; i <= b; i++) {
	if (sushu(i)) {
		s = to_string(i);
	}
	for (int j = 0; j < s.length(); j++) {
		if (s[j] - 48 == d) {
			sum++;
			break;
		}
	}
	s = " ";
}
cout << sum;
return 0;

}

bool sushu(int num) {

if (num <= 1)
	return false;
for (int i = 2; i * i <= num; i++) {
	if (num % i == 0)
		return false;
}
return true;

}