#include <bits/stdc++.h>
namespace shl {
    typedef long long ll;
    using std :: max;
    struct node {
        int x, y;
        bool operator <(const node &q) const {
            if (y != q.y) return y < q.y;
            return x < q.x;
        }
    } a[150010];
    int f[150010], n;
    inline int read() {
        int ret = 0, op = 1;
        char c = getchar();
        while (!isdigit(c)) {
            if (c == ‘-‘) op = -1; 
            c = getchar();
        }
        while (isdigit(c)) {
            ret = (ret << 3) + (ret << 1) + c - ‘0‘;
            c = getchar();
        }
        return ret * op;
    }
    int query(int x) {
        int l = 1, r = x;
        int ans = -1;
        while (l <= r) {
            int mid = l + r >> 1;
            if (a[mid].y < a[x].x) {
                ans = mid;
                l = mid + 1;
            }
            else r = mid - 1;
        }
        return ans;
    }
    int main() {
        n = read();
        for (register int i = 1; i <= n; ++i) {
            a[i].x = read(), a[i].y = read();
        }
        std :: sort(a + 1, a + n + 1);
        f[1] = a[1].y - a[1].x + 1;
        for (register int i = 2; i <= n; ++i) {
            int ret = query(i);
            if (ret == -1) f[i] = max(f[i - 1], a[i].y - a[i].x + 1);
            else  f[i] = max(f[i - 1], f[ret] + a[i].y - a[i].x + 1);
        }
        printf("%d\n", f[n]);
        return 0;
    }
};
int main() {
    shl :: main();
    return 0;
}