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

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    map<int,int> L;
    map<int,int,greater<>> R;
    for(int i=0; i<N; i++){
        int l,r; cin >> l >> r;
        L[l-N]++; R[r-1]++;
    }

    int maxl = -1e9,minr = 2e9;
    for(auto [k,v] : L){
        if(v >= 2) L[k+1] += v-1;
        if(v) maxl = max(maxl,k);
    }
    for(auto [k,v] : R){
        if(v >= 2) R[k-1] += v-1;
        if(v) minr = min(minr,k);
    }

    cout << max(0,minr-maxl+1) << endl;
}