Problem:
Score : 500 points

Problem Statement

There are N integers X_1, X_2, \cdots, X_N, and we know that A_i \leq X_i \leq B_i.
Find the number of different values that the median of X_1, X_2, \cdots, X_N can take.

Notes

The median of X_1, X_2, \cdots, X_N is defined as follows. Let x_1, x_2, \cdots, x_N be the result of sorting X_1, X_2, \cdots, X_N in ascending order.

If N is odd, the median is x_{(N+1)/2};

if N is even, the median is (x_{N/2} + x_{N/2+1}) / 2.

Constraints

2 \leq N \leq 2 \times 10^5

1 \leq A_i \leq B_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 B_1
A_2 B_2
:
A_N B_N

Output

Print the answer.

Sample Input 1

2
1 2
2 3

Sample Output 1

3

If X_1 = 1 and X_2 = 2, the median is \frac{3}{2};

if X_1 = 1 and X_2 = 3, the median is 2;

if X_1 = 2 and X_2 = 2, the median is 2;

if X_1 = 2 and X_2 = 3, the median is \frac{5}{2}.

Thus, the median can take three values: \frac{3}{2}, 2, and \frac{5}{2}.

Sample Input 2

3
100 100
10 10000
1 1000000000

Sample Output 2

9991

Solution in C++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>

/* snippet: useful macros and functions */
#define ARC(i, a, b) for(Int i = (a); i < (b); ++i)
#define RC(i, n) ARC(i, 0, n)
#define ARCH(i, a, b) for(Int i = (a) - 1; i >= (b); --i)
#define RCH(i, n) ARCH(i, n, 0)
#define ALL(v) v.begin(), v.end()
template<class T> T rng(const T &a, const T &b){ return a < b ? b - a : a - b; }
template<class T> void chmaxmin(T &a, const T &b, const T &(*f)(const T &, const T &)){ a = f(a, b); }
#define chmax(a, b) chmaxmin(a, b, std::max)
#define chmin(a, b) chmaxmin(a, b, std::min)

#if __has_include(<experimental/iterator>)
#include <experimental/iterator>
auto debug = std::experimental::make_ostream_joiner(std::cout, " ");
#endif

/* snippet: inf struct */
#if __cplusplus >= 201703
struct{ template<class T> constexpr operator T(){ return std::numeric_limits<T>::max(); } constexpr auto operator-(); } inf;
struct{ template<class T> constexpr operator T(){ return std::numeric_limits<T>::lowest(); } constexpr auto operator-(); } negative_inf;
constexpr auto decltype(inf)::operator-(){ return negative_inf; }
constexpr auto decltype(negative_inf)::operator-(){ return inf; }
#endif

/* snippet: modint library */
#if __cpp_concepts
template<std::signed_integral T, T MOD>
#else
template<class T, T MOD>
#endif
class Modint{
	T val;
public:
	Modint(T val = 0) : val(val % MOD + (val > 0 ? 0 : MOD)) {}
	operator T(){ return val; }
	Modint &operator+=(const Modint &a){ val += a.val; if(val >= MOD) val -= MOD; return *this; }
	Modint &operator-=(const Modint &a){ val -= a.val; if(val < 0) val += MOD; return *this; }
	Modint &operator*=(const Modint &a){ val = val * a.val % MOD; return *this; }
	void inverse(){T x[2]={MOD,val},a[2]={0,1};int i;for(i=0;x[!i];i^=1){a[i]-=x[i]/x[!i]*a[!i];x[i]=x[i]%x[!i];}if(!i)a[i]+= MOD;val=a[i];}
	Modint &operator/=(Modint a){ a.inverse(); return *this *= a; }
	friend Modint modpow(Modint a, int n){ Modint ret(1); while(n){ if(n & 1) ret *= a; a *= a; n >>= 1; } return ret; }
	friend Modint operator+(Modint a, const Modint &b){ return a += b; }
	friend Modint operator-(Modint a, const Modint &b){ return a -= b; }
	friend Modint operator*(Modint a, const Modint &b){ return a *= b; }
	friend Modint operator/(Modint a, const Modint &b){ return a /= b; }
	friend std::ostream &operator<<(std::ostream &os, const Modint &a){ return os << a.val; }
};

/* push n numbers and get i-th min */
/* to get min and 2nd min, declare K_th_min<T, 2> and use get<0>(), get<1>() */
#if __cplusplus >= 201703
template<class T, std::size_t K>
class K_th_min{
	friend class K_th_min<T, K + 1>;
	T val;
	K_th_min<T, K - 1> lower;
	void push_(T &x){ lower.push_(x); if(val > x) std::swap(val, x); }
public:
	K_th_min() : val(std::numeric_limits<T>::max()) {}
	void push(T x){ push_(x); }
	template<std::size_t I> T get(){ if constexpr(I == K - 1) return val; else return lower.template get<I>(); }
};
template<class T> class K_th_min<T, 0>{ friend class K_th_min<T, 1>; void push_(T &){} public: K_th_min(){} void push(T){} };
#endif

/* snippet: using declarations */
using Int = long long;
using std::cout;
using std::cin;
using std::endl;
using Mint = Modint<long long, 1000000007>;

int main(){
	Int n;
	cin >> n;
	std::vector<Int> a(n), b(n);
	RC(i, n){
		cin >> a[i] >> b[i];
	}
	if(n % 2 == 1){
		std::sort(ALL(a));
		std::sort(ALL(b));
		cout << b[n / 2] - a[n / 2] + 1 << endl;
	}else{
		RC(i, n){
			a[i] *= 2;
			b[i] *= 2;
		}
		std::sort(ALL(a));
		std::sort(ALL(b));
		cout << (b[n / 2] + b[n / 2 - 1]) / 2 - (a[n / 2] + a[n / 2 - 1]) / 2 + 1 << endl;
	}
}