#include <iostream>

using namespace std;

uint8_t d[130000000];

int main() {
  int l, r, m;
  cin >> l >> r >> m;
  for (int i = l; i <= r; ++i) {
    d[i % m / 8] |= 1 << i % m % 8;
  }

  int c = 0;
  for (int i = 0; i < 130000000; ++i) {
    for (int j = 0; j < 8; ++j) {
      if (d[i] << j >> 7) c++;
    }
  }
  cout << c << endl;
  return 0;
}