#include<stdio.h>
    #include<math.h>
    int main( )
    {
      int x=1;
      double pi=0.0,y=1,z=1;
      while(fabs(z)>=1e-6)
      {
      pi=pi+z;
      y=y+2;
      x=-x;
      z=x/y;
      }
      pi=pi*4;
      printf("pi=%10.8f",pi);
    }