样例都过不了居然A了？

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include<math.h>
using namespace std;
#define N 100
#define ll long long
#define MOD 1000000007

double n, k, a, b;

int main()
{
    cin >> n >> k >> a >> b;
    double ans , t1, t2, t3, t;
    printf("%.2lf\n", n/b-n/a);
    return 0;
}