#include <bits/stdc++.h>
using namespace std;
//#define LOCAL
#define fi first
#define se second
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define ALL(v) (v).begin(), (v).end()
#define BIT(x) (1LL << (x))
#define MASK(x, i) (((x) >> (i)) & 1)
#define FOR(i, a, b) for(int i = (a), _b = (b); i <= _b; ++ i)
#define FORD(i, b, a) for(int i = (b), _a = (a); i >= _a; -- i)
const string NAME = "BAITAP";
const long long INF = 1e18;
const int inf = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const int mod = 998244353;
const int mxN = 5e5 + 5;
int N;
vector<pair<long long, long long>> A(mxN);
void init(void){
cin >> N;
FOR(i, 1, N) cin >> A[i].fi >> A[i].se;
}
struct cmp{
bool operator() (const pair<long long, long long> &a, const pair<long long, long long> &b){
return a.fi != b.fi ? a.fi < b.fi : a.se > b.se;
}
};
void process(void){
sort(A.begin() + 1, A.begin() + 1 + N, cmp());
long long ans = -INF;
long long mx = -INF;
FOR(i, 1, N){
A[i].se += A[i - 1].se;
mx = max(A[i].fi - A[i - 1].se, mx);
ans = max(ans, A[i].se - A[i].fi + mx);
}
cout << ans;
}
signed main(void){
ios::sync_with_stdio(false);
cin.tie(nullptr);
#ifdef LOCAL
freopen((NAME + ".INP").c_str(), "r", stdin);
freopen((NAME + ".OUT").c_str(), "w", stdout);
#endif // I/O
init();
process();
cerr << "\nTime elapsed: " << TIME << "s.\n";
}
