#include
     
      #include
      
       int main(void){   int denominator,flag;   double item,pi;   flag=1;   denominator=1;   item=1.0;   pi=0;   while(fabs(item)>=0.0001){        item=flag*1.0/denominator;        pi=pi+item;        flag=-flag;        denominator=denominator+2;   }   pi=pi*4;   printf("pi=%.4f\n",pi);   return 0;}