#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define all(v) v.begin(), v.end()
using namespace std;
const int maxn = 5e5 + 5, oo = 1e18;
int st[maxn*4 + 5];
void build(int id, int l, int r, int vals[]){
if (l == r){
st[id] = vals[l];
return;
}
int mid = (l + r)/2;
build(id*2, l, mid, vals);
build(id*2+1, mid+1, r, vals);
st[id] = max(st[id*2], st[id*2+1]);
}
int get(int id, int l, int r, int ul, int ur){
if (l > ur || r < ul) return -oo;
if (ul <= l && r <= ur) return st[id];
int mid = (l + r)/2;
return max(get(id*2, l, mid, ul, ur), get(id*2+1, mid+1, r, ul, ur));
}
signed main(){
cin.tie(0) -> sync_with_stdio(0);
int n;
cin >> n;
pair<int, int> a[n+1];
int vals[n+1] = {0};
for (int i = 1; i <= n; i++){
cin >> a[i].fi >> a[i].se;
}
sort(a+1, a+1+n);
for (int i = 1; i <= n; i++){
swap(a[i].fi, a[i].se);
}
for (int i = 2; i <= n; i++){
a[i].fi += a[i-1].fi;
}
for (int i = 1; i <= n; i++){
vals[i] = a[i].fi - a[i].se;
}
build(1, 1, n, vals);
int mx = 0;
for (int i = 1; i <= n; i++){
mx = max(mx, get(1, 1, n, i, n) + a[i].se - a[i-1].fi);
}
cout << mx;
}
