cbj

/*
 Author: 曹北健
 Result: AC Submission_id: 4270695
 Created at: Sun Apr 03 2022 10:39:58 GMT+0800 (China Standard Time)
 Problem_id: 5486   Time: 31    Memory: 2720
*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
int main(){
    double enter, jifen, res, seedx, seedy, sup;
    int i, cnt = 0;
    srand(time(0));
    scanf("%lf", &enter);
    sup = 1.0;
    for(i = 1; i <= 150000; i++){
        seedx = 1.0 * (rand() % 32768) / 32768.0 * enter;
        seedy = 1.0 * (rand() % 32768) / 32768.0 * sup;
        if(exp(-((seedx + 0.5) * (seedx + 0.5))) > seedy)
            cnt++;
}
    jifen = (double)cnt / 150000.0 * enter * sup;
    res = exp(-jifen);
    printf("%.6lf", res);
    return 0;
}