#include <set>
#include <unordered_set>
#include <iostream>
#include <stack>
#include <string>
#include <sstream>
#include <vector>
#include <map>
#include <cmath>
#include <numeric>
#include <algorithm>
#include <queue>
#include <bitset>

#define INFL 100100100100100100
#define INF 1100100100
using namespace std;


int main() {
	long long b;
	cin >> b;
	long long c;
	cin >> c;
	long long br, bl, brr, bll;
	br = b + (c-2)/2;
	bl = b - c/2;
	brr = -b + (c-1)/2;
	bll = -b - (c-1)/2;
	if (br < brr || bl < bll) {
		swap(br, brr);
		swap(bl, bll);
	}
	cout << br - bl + 1 + brr - bll + 1 - (bl <= brr ? brr - bl + 1: 0) << endl;
	return 0;
}
#include <bits/stdc++.h>
using namespace std;

// #define int long long // intで書いたけど心配なときにlong longに変換する
struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) begin(v), end(v)
#define RALL(v) rbegin(v), rend(v)
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (ll i = (a); i >= (ll)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)
#define EACH(i, n) for (auto&& i : n)

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\n';

/* alias */
using ll = long long;
using ull = unsigned long long;
using uint = unsigned int;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using tiii = tuple<int, int, int>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using plglg = pair<ll, ll>;
using tlglglg = tuple<ll, ll, ll>;
using vs = vector<string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in() {int x; cin >> x; return x;}
inline ll IN() {ll x; cin >> x; return x;}
inline vs split(const string& t, char c) {vs v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b) {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b) {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p) {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x) {cout << x << endl;}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v) {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ") {REP(i, v.size()) cout << v[i] << (i != (ll)v.size() - 1 ? s : "\n");}
inline void yesno(bool ok, string yes = "Yes", string no = "No") {cout << (ok?yes:no) << endl;}


signed main() {
    //my-code
    ll N, D, H; cin >> N >> D >> H;
    vll d(N), h(N); REP(i, N) cin >> d[i] >> h[i];

    double ans = (double) 0.0;

    REP(i, N) {
        double x = 0.0;
        if (d[i] == D) {
            x = h[i];
        } else {
            x = h[i] - (h[i]-H)*d[i]*1.0/(d[i]-D);
        }
        chmax(ans, x);
    }

    cout << fixed << ans << endl;

    return 0;
}

// https://github.com/kurokoji/.cpp-Template/wiki テンプレートについて
// http://www.creativ.xyz/dump-cpp-652 dump()について
// https://gist.github.com/rigibun/7905920 色々