#include <bits/stdc++.h>
#define PI 3.14159265359
using namespace std;
const int64_t mod = 1e9 + 7;

int main() {
	int L, R, M;
	cin >> L >> R >> M;

	if (R < M) {
		cout << R - L + 1 << endl;
		return 0;
	}
	else {
		int r, l;
		r = R / M;
		l = L / M;

		if (r - l >= 2) {
			cout << M << endl;
			return 0;
		}
		else {
			cout << R - L + 1 << endl;
			return 0;
		}
	}
}