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

#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,b,a) for (int i = (b)-1; i >= (a); i--)
#define ITER(it,a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); it++)
#define FILL(a,value) memset(a, value, sizeof(a))

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;

const double PI = acos(-1.0);
const int INF = 1000 * 1000 * 1000 + 7;
const LL LINF = INF * (LL) INF;

const int MAX = 111;

int X[MAX], Y[MAX];
int DX[MAX], DY[MAX];
int n, m, p;



pair<double, int> E[MAX * MAX * MAX];


double timeTo(double a, double b)
{
	double ans = b - a;
	if (ans < 0)ans += 2 * n;
	return ans;
}s

bool ok(double x)
{
	int sz = 0;
	FOR(i, 0, p)
	{
		if (DX[i] == 0)
		{
			int id = i + 1;
			E[sz++] = MP(0, id);
		}
		else if (DX[i] > 0)
		{
			double cur = .0;
			double pos = X[i];
			while (cur < 3 * n)
			{
				if (timeTo(x) < timeTo(2 * n - x))
				{
					pos = x;
					cur += timeTo(x);
					E[sz++] = MP(cur, DX[i] > 0 ? i + 1 : -(i+1));
				}
			}
		}

	}
}

double solve()
{
	double l = .0;
	double r = n;

	FOR(i, 0, 60)
	{
		double m = (l + r) * .5;
		if (ok(m)) l = m;
		else r = m;
	}
	return l * m;
}

int main()
{
	//freopen("in.txt", "r", stdin);
	//ios::sync_with_stdio(false); cin.tie(0);
	scanf("%d%d", &n, &m);
	scanf("%d", &p);
	FOR(i, 0, p)
	{
		scanf("%d%d%d%d", X + i, Y + i, DX + i, DY + i);
	}
	double ans = 1e100;


	FOR(it, 0, 2)
	{

		FOR(it2, 0, 2)
		{

			ans = min(ans, solve());

			FOR(i, 0, p)
			{
				swap(X[i], Y[i]);
				swap(DX[i], DY[i]);
			}
		}

		FOR(i, 0, p)
		{
			X[i] = n - X[i];
			DX[i] = -DX[i];
		}
	}


	ans = min(ans, solve());
	printf("%.7f", ans);


}