#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#define int long long
using namespace std;
pair<int,int> a[500001],b[500001];
int seg[1<<19][2];
int N,Left,Right,W;
void Update(int Pos, int V){
int ind = Pos + N - 1;
seg[ind][W] = V;
while(ind /= 2) seg[ind][W] = max(seg[ind * 2][W], seg[ind * 2 + 1][W]);
}
int Query(int l = 1, int r = N, int ind = 1){
if(l > Right or r < Left) return -1e18;
if(l >= Left && r <= Right) return seg[ind][W];
int mid = (l + r) / 2;
return max(Query(l, mid, ind * 2), Query(mid + 1, r, ind * 2 + 1));
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n, ans = 0; cin >> n;
N = exp2(ceil(log2(n)));
for(int i = 0; i < n; i++){
cin >> a[i].first >> a[i].second;
}
sort(a,a+n);
for(int i = 0; i < n; i++){
if(i) a[i].second += a[i - 1].second;
b[i].first = a[i].second - a[i].first;
b[i].second = (i == 0 ? 0 : -a[i - 1].second) + a[i].first;
W = 0;
Update(i + 1, b[i].first);
W = 1;
Update(i + 1, b[i].second);
}
for(int i = 0; i < n; i++){
Left = 1; Right = i;
W = 1;
ans = max(ans, b[i].first + Query());
Left = i + 2; Right = n;
W = 0;
ans = max(ans, b[i].second + Query());
}
cout << ans;
return 0;
}
/*
*/
