#define _GLIBCXX_DEBUG
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(i64 i=0; i<(i64)(n); i++)
#define repr(i,n) for(i64 i=(i64)(n)-1; i>=0; i--)
const i64 INF = 1001001001001001001;
const char* yn(bool x){ return x ? "Yes" : "No"; }
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; }
using namespace std;


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
}

}


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));
}

}

void testcase(){
    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;
        i64 q = dec.queryNoLessThan(l);
        if(N <= q || r < q){ cout << "0\n"; return; }
        dec.dec(q);
    }
    cout << max(0, y-x+1) << endl;
}

int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    #ifdef NACHIA
    int T; cin >> T; for(int t=0; t<T; T!=++t?(cout<<'\n'),0:0)
    #endif
    testcase();
    return 0;
}