#include<bits/stdc++.h>
#define X first
#define Y second
#define all(x) begin(x), end(x)
#define FOR(i, a, b) for(int i = (a); i <= (b); i++)
#define FORD(i, b, a) for(int i = (b); i >= (a); i--)
#define REP(i, a, b) for (int i = (a); i < (b); i++)
#define mxx max_element
#define mnn min_element
#define SQR(x) (1LL * (x) * (x))
#define MASK(i) (1LL << (i))
#define Point Vector
#define left Left
#define right Right
#define div Div
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
typedef pair<db, db> pdb;
typedef pair<ld, ld> pld;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;
typedef pair<ll, ll> pll;
typedef pair<ll, pll> plll;
typedef pair<ll, int> pli;
typedef pair<ll, pii> plii;
template<class A, class B>
bool maximize(A& x, B y) {
if (x < y) return x = y, true; else return false;
}
template<class A, class B>
bool minimize(A& x, B y) {
if (x > y) return x = y, true; else return false;
}
/* END OF TEMPLATE */
const int N = 1e6 + 7;
pll a[N];
ll pre[N];
int n;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n;
FOR(i, 1, n) cin>>a[i].X>>a[i].Y;
sort(a + 1, a + 1 + n);
FOR(i, 1, n) pre[i] = pre[i - 1] + a[i].Y;
ll Max = -9e18, res = -9e18;
FOR(i, 1, n) {
maximize(Max, -pre[i - 1] + a[i].X);
maximize(res, pre[i] - a[i].X + Max);
}
cout<<res;
return 0;
}
