/* 

sum1.c 

compute sum = atan(1) + atan(2) + ... + atan(n)

*/

#include <stdio.h> 
#include <assert.h> 
#include <math.h> 

#include <omp.h> 


int main(int argc, char** argv) {

  long n  = atol(argv[1]); 
  double  sum; 
  long  i; 
  double t1, t2; 
  
  //initialize sum 
  sum = 0; 

  t1 = omp_get_wtime(); 
  
  printf("Start. ");

  for (i=0; i<n; i++) {
    sum = sum + atan(i); 
  }

  t2 = omp_get_wtime();   

  printf("sum=%.1f ", sum);
  printf("Done. time = %.1f\n",  t2-t1);
  
  return 0; 
}