#include <stdio.h>

  #include <stdlib.h>

  #include <string.h>

  #include <mpi.h>

  #define N 1000000000

  
  int main (int argc, char** argv)
  {
      int rank;
      int size;
      long long int n;
      long long int i;
  
      double l_sum,total_sum, x, h;
  
      MPI_Init(NULL, NULL);
     
      MPI_Comm_size(MPI_COMM_WORLD, &size);
      MPI_Comm_rank(MPI_COMM_WORLD, &rank);
      
      n=N;
  
      if(rank==0)
      {
          if(argc==2)
          {

           n = atol(argv[1]);

          }
  
          printf("MPI version with process = %d
  ", size);
          printf("Number of intervals: %lld
  ", n);
      }

    MPI_Bcast(&n, 1, MPI_LONG, 0, MPI_COMM_WORLD);

      
  
      h = 1.0/n;
  
      l_sum = 0.0;
  
      for (i = rank; i < n; i += size)
      {
          x = (i + 0.5)*h;
          l_sum += 4.0/(1.0 + x*x);
      }
  
      l_sum *= h;
  
      MPI_Reduce(&l_sum,&total_sum,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD);
      
      if(rank==0)
      {

          printf("Pi=%0.20g
  ", total_sum);

  
      }
  
      MPI_Finalize();
      return 0;
  }