/* * Create by : KhacTrungLTQB * Create Time: 2022-09-07 21:19:20 * Modified time: 2022-10-22 07:23:12 * Description: Nothing */ #include <bits/stdc++.h> using namespace std; #define fio(l, r) for (int i = l; i <= r; i++) #define fjo(l, r) for (int j = l; j <= r; j++) #define ll long long #define str string #define en cout << endl; #define db double ll a[10000], b[10000], l[10000]; void qsort(ll l, ll r) { ll i = l, j = r, x = b[(l + r) / 2]; while (i <= j) { while (b[i] < x) i++; while (b[j] > x) j--; if (i <= j) { swap(a[i], a[j]); swap(b[i], b[j]); i++; j--; } } if (l < j) qsort(l, j); if (i < r) qsort(i, r); } int main() { ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); ifstream fii("XEPPHONG.inp"); ofstream foo("XEPPHONG.out"); ll n; cin >> n; fio(1, n) cin >> a[i] >> b[i]; qsort(1, n); fio(1, n) l[i] = b[i] - a[i]; fio(2, n) fjo(1, i - 1) if (a[i] >= b[j]) l[i] = max(l[i], l[j] + (b[i] - a[i])); ll MAX = 0; fio(1, n) MAX = max(MAX, l[i]); cout << MAX; foo.close(); }