#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <class T>
using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#ifndef Local
#pragma GCC optimize("O3,unroll-loops")
#endif
#define int long long
#define ll long long
#define vi vector<int>
#define vvi vector<vi>
#define pii pair<int, int>
#define vpi vector<pii>
#define vvpi vector<vpi>
#define vb vector<bool>
#define vvb vector<vb>
#define endl '\n'
#define sp <<' '<<
#define F(i, s, n) for(int i = s; i < (int) n; i++)
#define pb push_back
#define fi first
#define se second
const int mod = 998244353;
const int inf = 1e12;
const int N = 2e5+5;
void solve() {
int n;
cin >> n;
vpi a(n+1, {0, 0});
F(i, 1, n+1) cin >> a[i].fi >> a[i].se;
sort(a.begin()+1, a.end());
F(i, 2, n+1) a[i].se += a[i-1].se;
int ans = -inf;
int mx = -inf;
F(i, 1, n+1) {
mx = max(mx, -a[i-1].se + a[i].fi);
ans = max(ans, a[i].se - a[i].fi + mx);
}
cout << ans << endl;
}
void setIO() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Local
freopen("local.in", "r", stdin);
freopen("local.out", "w", stdout);
#else
// freopen("friendcross.in","r",stdin);
// freopen("friendcross.out","w",stdout);
#endif
}
signed main() {
setIO();
int t = 1;
//cin >> t;
while(t--) solve();
}
