#include <stdio.h>
int main(){
  int x, y, l, k, c=0;
  scanf("%d%d%d", &x, &y, &l);
  c += y < 0 ? 2 : 0;
  x = ~~x; y = ~~y;
  for(k = 0; k < x;k+=l,c++);
  for(k = 0; k < y;k+=l,c++);
  if(x!=0) c++;
  printf("%d\n", c);
  return 0;
}