lianxi`#include<stdio.h> int main (void){ int length; double

int main (void){
  int length;
  double sum = 0.0 ;
  printf ("Enter the limit length:");
  scanf("%d",&length);
  while(length>0){
    sum = 0.0;
    for (int i= 1 ;i <= length; i++){
         sum = sum +1.0/i;
    }
    printf("The sum for 1.0 +...+1.0/%d.0 is %lf\n",length,sum);
    sum = 0.0;
    for(int i = 1 ;i <=length;i++){
      if(i%2==0) sum =sum - 1.0/i;
      else sum = sum +1.0/i;
  }
  printf("The sum for 1.0-...+1.0/%d.0 is %lf\n",length,sum);

  sum = 0.0;
  for (int i= 1;i <= length;i++){
      if (i%2 != 0) sum = sum + 2*1.0/i;
      }
      printf("The sum for 1.0 +1.0+2.0/3.0+...+2.0/%d.0 is %lf\n",length,sum);
      printf("Enter the limit length:");
      scanf("%d",&length);
  }
  printf("\nDone!\n");
  return 0;

      
}