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

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

void main(void)
{
  int    seed;
  int    j;
  int    ntrial;
  int    n1 = 0;
  double x0, y0;
  double s;

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

  srand(seed);
  for (j = 1; j <= ntrial; j ++) {
    x0 = RAND();
    y0 = RAND();
    if (y0 < exp(-x0)) {
      n1 = n1 + 1;
    }
  }
  s = (double)n1 / ntrial;
  printf("s = %1.6f \n", s);
}