#include <bits/stdc++.h>
using namespace std;
# define int long long
# define fir first
# define sec second
# define pb push_back
const int cnst = 5e5+5;
bool mutipletestcase = 0;
//bool debug = false;
int arr[cnst];
int posi[cnst*4];
int merge(int a, int b) {
return max(a, b);
}
void build(int a, int b, int id) {
if(a == b) {posi[id] = arr[a]; return;}
int mid = (a+b)/2;
build(a, mid, id*2);
build(mid+1, b, id*2+1);
posi[id] = merge(posi[id*2], posi[id*2+1]);
}
void update(int a, int b, int id, int pos, int val) {
if(a == pos && b == pos) {
posi[id] = val;
return;
}
int mid =(a+b)/2;
if(pos <= mid) update(a, mid, id*2, pos, val);
else update(mid+1, b, id*2+1, pos, val);
posi[id] = merge(posi[id*2], posi[id*2+1]);
}
int get(int a, int b, int id, int from, int to) {
if(to < a || from > b) return 0;
if(from <= a && b <= to) return posi[id];
int mid = (a+b)/2;
return merge(get(a, mid, id*2, from, to), get(mid+1, b, id*2+1, from, to));
}
void solve() {
int n; cin >> n;
pair<int, int> paint[n+5];
for(int i = 1; i<=4*n; i++) posi[i] = LONG_MIN;
for(int i = 1; i<=n; i++) cin >> paint[i].fir >> paint[i].sec;
int presum[n+5]; presum[0] = 0;
sort(paint+1, paint+n+1);
for(int i = 1; i<=n; i++) {
presum[i] = presum[i-1]+paint[i].sec;
update(1, n, 1, i, presum[i]-paint[i].fir);
}
int ans = 0;
for(int i = 1; i<=n; i++) {
int temp = paint[i].fir-presum[i-1];
temp += get(1, n, 1, i, n);
ans = max(ans, temp);
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(false);
int t = 1;
if(mutipletestcase) cin >> t;
while(t--) solve();
}
