// L , R それぞれ値域を 0 ... N-1 にしてからソートすればボトルネックではなくなる説

#include <cstdio>
#include <cctype>
#include <cstdint>
#include <string>

namespace nachia{

struct CInStream{
private:
	static const unsigned int INPUT_BUF_SIZE = 1 << 17;
	unsigned int p = INPUT_BUF_SIZE;
	static char Q[INPUT_BUF_SIZE];
public:
	using MyType = CInStream;
	char seekChar(){
		if(p == INPUT_BUF_SIZE){
			size_t len = fread(Q, 1, INPUT_BUF_SIZE, stdin);
			if(len != INPUT_BUF_SIZE) Q[len] = '\0';
			p = 0;
		}
		return Q[p];
	}
	void skipSpace(){ while(isspace(seekChar())) p++; }
private:
	template<class T, int sp = 1>
	T nextUInt(){
		if constexpr (sp) skipSpace();
		T buf = 0;
		while(true){
			char tmp = seekChar();
			if('9' < tmp || tmp < '0') break;
			buf = buf * 10 + (tmp - '0');
			p++;
		}
		return buf;
	}
public:
	uint32_t nextU32(){ return nextUInt<uint32_t>(); }
	int32_t nextI32(){
		skipSpace();
		if(seekChar() == '-'){
			p++; return (int32_t)(-nextUInt<uint32_t, 0>());
		}
		return (int32_t)nextUInt<uint32_t, 0>();
	}
	uint64_t nextU64(){ return nextUInt<uint64_t>();}
	int64_t nextI64(){
		skipSpace();
		if(seekChar() == '-'){
			p++; return (int64_t)(-nextUInt<int64_t, 0>());
		}
		return (int64_t)nextUInt<int64_t, 0>();
	}
	template<class T>
	T nextInt(){
		skipSpace();
		if(seekChar() == '-'){
			p++;
			return - nextUInt<T, 0>();
		}
		return nextUInt<T, 0>();
	}
	char nextChar(){ skipSpace(); char buf = seekChar(); p++; return buf; }
	std::string nextToken(){
		skipSpace();
		std::string buf;
		while(true){
			char ch = seekChar();
			if(isspace(ch) || ch == '\0') break;
			buf.push_back(ch);
			p++;
		}
		return buf;
	}
	MyType& operator>>(unsigned int& dest){ dest = nextU32(); return *this; }
	MyType& operator>>(int& dest){ dest = nextI32(); return *this; }
	MyType& operator>>(unsigned long& dest){ dest = nextU64(); return *this; }
	MyType& operator>>(long& dest){ dest = nextI64(); return *this; }
	MyType& operator>>(unsigned long long& dest){ dest = nextU64(); return *this; }
	MyType& operator>>(long long& dest){ dest = nextI64(); return *this; }
	MyType& operator>>(std::string& dest){ dest = nextToken(); return *this; }
	MyType& operator>>(char& dest){ dest = nextChar(); return *this; }
} cin;

struct FastOutputTable{
	char LZ[1000][4] = {};
	char NLZ[1000][4] = {};
	constexpr FastOutputTable(){
		using u32 = uint_fast32_t;
		for(u32 d=0; d<1000; d++){
			LZ[d][0] = ('0' + d / 100 % 10);
			LZ[d][1] = ('0' + d /  10 % 10);
			LZ[d][2] = ('0' + d /   1 % 10);
			LZ[d][3] = '\0';
		}
		for(u32 d=0; d<1000; d++){
			u32 i = 0;
			if(d >= 100) NLZ[d][i++] = ('0' + d / 100 % 10);
			if(d >=  10) NLZ[d][i++] = ('0' + d /  10 % 10);
			if(d >=   1) NLZ[d][i++] = ('0' + d /   1 % 10);
			NLZ[d][i++] = '\0';
		}
	}
};

struct COutStream{
private:
	using u32 = uint32_t;
	using u64 = uint64_t;
	using MyType = COutStream;
	static const u32 OUTPUT_BUF_SIZE = 1 << 17;
	static char Q[OUTPUT_BUF_SIZE];
	static constexpr FastOutputTable TB = FastOutputTable();
	u32 p = 0;
	static constexpr u32 P10(u32 d){ return d ? P10(d-1)*10 : 1; }
	static constexpr u64 P10L(u32 d){ return d ? P10L(d-1)*10 : 1; }
	template<class T, class U> static void Fil(T& m, U& l, U x){ m = l/x; l -= m*x; }
public:
	void next_dig9(u32 x){
		u32 y;
		Fil(y, x, P10(6));
		nextCstr(TB.LZ[y]);
		Fil(y, x, P10(3));
		nextCstr(TB.LZ[y]); nextCstr(TB.LZ[x]);
	}
	void nextChar(char c){
		Q[p++] = c;
		if(p == OUTPUT_BUF_SIZE){ fwrite(Q, p, 1, stdout); p = 0; }
	}
	void nextEoln(){ nextChar('\n'); }
	void nextCstr(const char* s){ while(*s) nextChar(*(s++)); }
	void nextU32(uint32_t x){
		u32 y = 0;
		if(x >= P10(9)){
			Fil(y, x, P10(9));
			nextCstr(TB.NLZ[y]); next_dig9(x);
		}
		else if(x >= P10(6)){
			Fil(y, x, P10(6));
			nextCstr(TB.NLZ[y]);
			Fil(y, x, P10(3));
			nextCstr(TB.LZ[y]); nextCstr(TB.LZ[x]);
		}
		else if(x >= P10(3)){
			Fil(y, x, P10(3));
			nextCstr(TB.NLZ[y]); nextCstr(TB.LZ[x]);
		}
		else if(x >= 1) nextCstr(TB.NLZ[x]);
		else nextChar('0');
	}
	void nextI32(int32_t x){
		if(x >= 0) nextU32(x);
		else{ nextChar('-'); nextU32((u32)-x); }
	}
	void nextU64(uint64_t x){
		u32 y = 0;
		if(x >= P10L(18)){
			Fil(y, x, P10L(18));
			nextU32(y);
			Fil(y, x, P10L(9));
			next_dig9(y); next_dig9(x);
		}
		else if(x >= P10L(9)){
			Fil(y, x, P10L(9));
			nextU32(y); next_dig9(x);
		}
		else nextU32(x);
	}
	void nextI64(int64_t x){
		if(x >= 0) nextU64(x);
		else{ nextChar('-'); nextU64((u64)-x); }
	}
	template<class T>
	void nextInt(T x){
		if(x < 0){ nextChar('-'); x = -x; }
		if(!(0 < x)){ nextChar('0'); return; }
		std::string buf;
		while(0 < x){
			buf.push_back('0' + (int)(x % 10));
			x /= 10;
		}
		for(int i=(int)buf.size()-1; i>=0; i--){
			nextChar(buf[i]);
		}
	}
	void writeToFile(bool flush = false){
		fwrite(Q, p, 1, stdout);
		if(flush) fflush(stdout);
		p = 0;
	}
	COutStream(){ Q[0] = 0; }
	~COutStream(){ writeToFile(); }
	MyType& operator<<(unsigned int tg){ nextU32(tg); return *this; }
	MyType& operator<<(unsigned long tg){ nextU64(tg); return *this; }
	MyType& operator<<(unsigned long long tg){ nextU64(tg); return *this; }
	MyType& operator<<(int tg){ nextI32(tg); return *this; }
	MyType& operator<<(long tg){ nextI64(tg); return *this; }
	MyType& operator<<(long long tg){ nextI64(tg); return *this; }
	MyType& operator<<(const std::string& tg){ nextCstr(tg.c_str()); return *this; }
	MyType& operator<<(const char* tg){ nextCstr(tg); return *this; }
	MyType& operator<<(char tg){ nextChar(tg); return *this; }
} cout;

char CInStream::Q[INPUT_BUF_SIZE];
char COutStream::Q[OUTPUT_BUF_SIZE];

} // namespace nachia
#include <vector>

namespace nachia{

int Popcount(unsigned long long c) noexcept {
#ifdef __GNUC__
    return __builtin_popcountll(c);
#else
    c = (c & (~0ull/3)) + ((c >> 1) & (~0ull/3));
    c = (c & (~0ull/5)) + ((c >> 2) & (~0ull/5));
    c = (c & (~0ull/17)) + ((c >> 4) & (~0ull/17));
    c = (c * (~0ull/257)) >> 56;
    return c;
#endif
}

// please ensure x != 0
int MsbIndex(unsigned long long x) noexcept {
#ifdef __GNUC__
    return 63 - __builtin_clzll(x);
#else
    using u64 = unsigned long long;
    int q = (x >> 32) ? 32 : 0;
    auto m = x >> q;
    constexpr u64 hi = 0x8888'8888;
    constexpr u64 mi = 0x1111'1111;
    m = (((m | ~(hi - (m & ~hi))) & hi) * mi) >> 35;
    m = (((m | ~(hi - (x & ~hi))) & hi) * mi) >> 31;
    q += (m & 0xf) << 2;
    q += 0x3333'3333'2222'1100 >> (((x >> q) & 0xf) << 2) & 0xf;
    return q;
#endif
}

// please ensure x != 0
int LsbIndex(unsigned long long x) noexcept {
#ifdef __GNUC__
    return __builtin_ctzll(x);
#else
    return MsbIndex(x & -x);
#endif
}

}

#include <algorithm>

namespace nachia {

struct DsuFast{
private:
    std::vector<int> w;
public:
    DsuFast(int n = 0) : w(n, -1) {}
    int leader(int u){
        if(w[u] < 0) return u;
        return w[u] = leader(w[u]);
    }
    int operator[](int u){ return leader(u); }
    int merge(int u, int v){
        u = leader(u);
        v = leader(v);
        if(u == v) return u;
        if(-w[u] < -w[v]) std::swap(u, v);
        w[u] += w[v];
        w[v] = u;
        return u;
    }
    int size(int u){ return -w[leader(u)]; }
    bool same(int u, int v){ return leader(u) == leader(v); }
};

} // namespace nachia

namespace nachia {

struct DecrementalPredecessorQuery{
private:
    int n;
    int b;
    std::vector<unsigned long long> X;
    nachia::DsuFast Y;
    std::vector<int> dsuTrans;
    int smallQ(int c, int d) const noexcept {
        auto z = X[c] & ((~0ull) << d);
        return z ? c*64 + LsbIndex(z) : -1;
    }
    int largeQ(int c) noexcept { return dsuTrans[Y.leader(c)]; }
public:
    DecrementalPredecessorQuery(int _n)
        : n(_n+2), b(n/64+2), X(b, ~0ull), Y(b), dsuTrans(b)
    {
        for(int i=0; i<b; i++) dsuTrans[i] = i;
    }
    // remove token i
    void dec(int i){
        i++;
        int c = i/64, d = i%64;
        X[c] &= ~(1ull << d);
        if(X[c] == 0){
            int h = largeQ(c+1);
            dsuTrans[Y.merge(c, c+1)] = h;
        }
    }
    // minimum token left x : i <= x
    int queryNoLessThan(int i){
        if(n <= i) return n;
        if(i < 0) i = 0;
        i++;
        int c = i/64, d = i%64;
        int x = smallQ(c, d);
        if(x >= 0) return x-1;
        c = largeQ(c+1); d = 0;
        return smallQ(c, d)-1;
    }
};

} // namespace nachia

#include <cassert>

namespace nachia{

template<class Iterator>
void EnsurePermutation(Iterator first, Iterator last){
    int n = std::distance(first, last);
    std::vector<int> vis(n, 0);
    for(Iterator i=first; i!=last; i++){
        assert(0 <= *i);
        assert(*i < n);
        assert(vis[*i] == 0);
        vis[*i] = 1;
    }
}

template<class T> std::vector<T> Permute(
    const std::vector<T>& src,
    const std::vector<int>& perm
){
    const bool DEBUG = true;
    int n = src.size();
    if constexpr (DEBUG){
        assert(perm.size() == src.size());
        EnsurePermutation(perm.begin(), perm.end());
    }
    std::vector<T> res;
    res.reserve(n);
    for(int i=0; i<n; i++) res.push_back(src[perm[i]]);
    return res;
}

template<class T> std::vector<T>& PermuteInPlace(
    std::vector<T>& src,
    std::vector<int> perm
){
    const bool DEBUG = true;
    int n = src.size();
    if constexpr (DEBUG){
        assert(perm.size() == src.size());
        EnsurePermutation(perm.begin(), perm.end());
    }
    for(int s=0; s<n; s++){
        int p = s;
        while(perm[p] != s){
            std::swap(src[p], src[perm[p]]);
            std::swap(p, perm[p]);
        }
        perm[p] = p;
    }
    return src;
}

// stable sort
std::vector<int> BucketSortPermutation(
    std::vector<int>::const_iterator first,
    std::vector<int>::const_iterator last,
    int maxVal
){
    const bool DEBUG = true;
    int n = last - first;
    if constexpr (DEBUG){
        for(auto itr = first; itr != last; itr++){
            assert(0 <= *itr);
            assert(*itr <= maxVal);
        }
    }
    std::vector<int> cnt(maxVal+2);
    std::vector<int> res(n);
    for(int i=0; i<n; i++) cnt[first[i]+1]++;
    for(int i=0; i<maxVal; i++) cnt[i+1] += cnt[i];
    for(int i=0; i<n; i++) res[cnt[first[i]]++] = i;
    return res;
}

// stable sort
template<class T, class Mapping>
std::vector<int> BucketSortPermutation(
    typename std::vector<T>::const_iterator first,
    typename std::vector<T>::const_iterator last,
    const Mapping& f,
    int maxVal
){
    std::vector<int> buf(last - first);
    auto bufitr = buf.begin();
    for(auto itr = first; itr != last; itr++, bufitr++) *bufitr = f(*itr);
    return BucketSortPermutation(buf.begin(), buf.end(), maxVal);
}

// stable sort
template<class T, class Mapping>
std::vector<T> BucketSort(
    std::vector<T> src,
    const Mapping& f,
    int maxVal
){
    return PermuteInPlace(src, BucketSortPermutation<T>(src.begin(), src.end(), f, maxVal));
}

// stable sort
template<class Iter, class Mapping>
std::vector<int> BucketSortPermutation(
    Iter first,
    Iter last,
    const Mapping& f,
    int maxVal
){
    std::vector<int> buf(std::distance(first, last));
    auto bufitr = buf.begin();
    for(auto itr = first; itr != last; itr++, bufitr++) *bufitr = f(*itr);
    return BucketSortPermutation(buf.begin(), buf.end(), maxVal);
}

template<class Iter> void PermuteInPlace(
    Iter srcFirst,
    Iter srcLast,
    std::vector<int> perm
){
    const bool DEBUG = true;
    int n = std::distance(srcFirst, srcLast);
    if constexpr (DEBUG){
        assert(perm.size() == (size_t)n);
        EnsurePermutation(perm.begin(), perm.end());
    }
    for(int s=0; s<n; s++){
        int p = s;
        while(perm[p] != s){
            std::swap(srcFirst[p], srcFirst[perm[p]]);
            std::swap(p, perm[p]);
        }
        perm[p] = p;
    }
}

// stable sort
template<class Iter, class Mapping>
void BucketSort(
    Iter destFirst,
    Iter destLast,
    const Mapping& f,
    int maxVal
){
    PermuteInPlace(destFirst, destLast, BucketSortPermutation(destFirst, destLast, f, maxVal));
}

}
#include <utility>
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define repr(i,n) for(int i=(int)(n)-1; i>=0; i--)
template<class A, class B> void chmin(A& l, const B& r){ if(r < l) l = r; }
template<class A, class B> void chmax(A& l, const B& r){ if(l < r) l = r; }

int main(){
    using nachia::cin;
    using nachia::cout;
    using namespace std;
    int N; cin >> N;
    vector<int> L(N), R(N);
    rep(i,N){ cin >> L[i] >> R[i]; L[i]--; R[i]--; }
    int ld = 0; {
        ld = *max_element(L.begin(), L.end()) - (N-1);
        rep(i,N){ L[i] -= ld; chmax(L[i], 0); }
    }
    int rd = 0; {
        rd = *min_element(R.begin(), R.end());
        rep(i,N){ R[i] -= rd; chmin(R[i], N-1); }
    }

    int rmin = *min_element(R.begin(), R.end());
    auto IL = nachia::BucketSortPermutation(L.begin(), L.end(), N-1);
    auto IR = nachia::BucketSortPermutation(R.begin(), R.end(), N-1);
    int x = -1001001001; rep(i,N) chmax(x, L[IL[i]] + ld - i);
    int y =  1001001001; rep(i,N) chmin(y, R[IR[i]] + rd - i);

    int f = true;
    auto dec = nachia::DecrementalPredecessorQuery(N);
    for(auto i : IR){
        int l = L[i] + ld - x, r = R[i] + rd - x;
        int q = dec.queryNoLessThan(l);
        if(N <= q || r < q){ cout << "0\n"; return 0; }
        dec.dec(q);
    }
    cout << max(0, y-x+1) << '\n';
    return 0;
}