#include <stdio.h>


int main()
{
  int a, b;
  printf("enter a and b:\n");
  scanf("%d %d", &a, &b);

  if (a > b)
  {
    return 0;
  }

  double result = 0;

  int i;
  for (i = a; i <= b; i++)
  {
    double i2 = (double) i;
    result = result + 1.0/i2;
  }

  printf("the sum is %lf\n", result);
}