#include<stdio.h>
  int main()
  {
    int sign = 1;
    double deno = 2.0, sum = 1.0, term;//deno分母，sum多项式，term分式
    while (deno <= 100)
    {
      sign = -sign;
      term = sign / deno;
      sum = sum + term;
      deno = deno + 1;
    }
    for(int deno=1;deno<=100;deno++){
      sign = -sign;
      term = sign / deno;
      sum += term;    
    }
    printf("%f\n",sum);
    return 0;
  }