#include <stdio.h>
  #include <string.h>
  #include <stdlib.h>
  
  #define N 100000000
  
  int main (int argc, char** argv)
  {
      int task_id;
      int total_tasks;
      long long int n;
      long long int i;
  
      double l_sum, x, h;
  
      n=N;
  
      if(argc<3)
      {
          fprintf(stderr,"Usage : %s task_id total_tasks [n]
  ",argv[0]);
          exit(0);
      }
  
      task_id = atoi(argv[1]);
      total_tasks = atoi(argv[2]);
      
      if(argc==4)
      {
          n = atoll(argv[3]);
      }
  
      fprintf(stderr, "task_id=%d total_tasks=%d n=%lld
  ", task_id, total_tasks, n);
  
      h = 1.0/n;
  
      l_sum = 0.0;
  
      for (i = task_id; i < n; i += total_tasks)
      {
          x = (i + 0.5)*h;
          l_sum += 4.0/(1.0 + x*x);
      }
  
      l_sum *= h;
  
      printf("Pi=%0.12g
  ", l_sum);
  
      return 0;
  }