#includ<stdio.h>
int main()
{
  int a, b, c, n=0, m=1;
  scanf("%d %d %d", &a, &b, &c);
  if(1 <= a <= 10000 && 1 <= b <= 10000 && 1 <= c <= 10000 && a<=b){
    for(n = (a / c) + 1;b < n*c ;n++){
      m++;
    
    }
  }
  printf("%d\n",m);
  return 0;
}    