/* 
 *         　　exp 定積分 その２
 */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#define RAND()    ((double)rand() / (1.0 + RAND_MAX))

int main(void)
{
  int    seed;
  int    j;
  int    ntrial;
  double y0;
  double s = 0.0;
  double sreal, serror;

  printf("Input: Number of trials:\n");
  scanf("%u", &ntrial);
  printf("Input: seed\n");
  scanf("%u", &seed);

  srand(seed);
  for (j = 1; j <= ntrial; j ++) {
    y0 = exp(-RAND());
    s = s + y0;
  }
  s = s / ntrial;
  sreal=1.0-exp(-1.0);
  serror=s-sreal;
  printf("s = %1.10f \n", s);
  printf("sreal = %1.10f \n", sreal);
  printf("serror = %1.10f \n", serror);
}