#!/usr/bin/env tcc
#include <stdio.h>

double f(double x) {
  return 1 / x;
}

int main(void) {
  int a = 1;
  int b = 2;

  double sum = 0;
  double dx = (double)(b - a) / 1e3;
  double x;

  for (x = a; x <= b; x += dx) {
    sum += f(x) * dx;
  }

  printf("%lf\n", sum);
  return 0;
}