/* https://yukicoder.me/problems/no/810 */

#include <iostream>
#include <vector>

/* {{{ Variables */
int L, R, M;
/* }}} */

int main(int argc, char *argv[])
{
  /* {{{ Input */
  std::cin >> L >> R >> M;
  /* }}} */

  /* {{{ Output */
  int tmp = (R-L+1)/M;
  if (tmp == 0) {
    tmp = (R-L+1)%M;
  }
  std::cout << tmp << std::endl;
  /* }}} */

  return 0;
}