Untitled

#include <bits/stdc++.h>
using namespace std;

double px[20], py[20];
double d, g = 1.0, pi = acos(-1.0);
int n, b;

bool possible(double v, double R) {
    if(v * v < R * g) return 0;

    double theta = 0.5 * asin(R * g / (v * v));
    theta = max(pi/2 - theta, theta);

    for(int i = 0; i < n; i++) {
        double x = px[i] - floor(px[i]/R) * R;

        double y = x * tan(theta) - g * x * x/(2.0*v*v*cos(theta)*cos(theta));

        if(y < py[i]) return 0; 
    }
    return 1;
}

int main()
{
    cin >> d >> n >> b;
    b++;

    for(int i = 0; i < n; i++) cin >> px[i] >> py[i];

    double ans = 2e9+10;

    for(int bounce = 1; bounce <= b; bounce++) {
        double R = d/bounce;
        double anshere = 2e9+15;

        double lo = 0, hi = 2e5;
        while((hi - lo) > 0.0000001) {
            double mid = (lo + hi) / 2;
            if(possible(mid, R)) {
                anshere = mid;
                hi = mid;
            }
            else lo = mid;
        }

        ans = min(ans, anshere);
    }

    cout << fixed << setprecision(10) << ans << endl;

    return 0;
}