C语言编程题：求1-1/2+1/3_1/4+1/5.....前30项的和。

#include<stdio.h>
int main()
{int i=1;
float s=0;
while(i<=30)
{if(i%2)s+=1.0/i;
else s-=1.0/i;
i++;
}
printf("%f\n",s);
return 0;
}