#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
typedef long long ll;
using namespace __gnu_pbds;
#define endl '\n'
#define hitaf ios_base::sync_with_stdio(false); cin.tie(0);
#define fi first
#define se second
template <typename T>
using ordered_set = tree<T,null_type,less<T>,rb_tree_tag, tree_order_statistics_node_update>;
const ll MOD = 1e9 + 7;
const ll MOD1 = 998244353;
const ll INF = 4500000000000000000LL;
const ll mod1 = 6900000469;
const ll mod2 = 698000002369;
ll n, m, q, k, a[1200005], b[500005], c[500005], st[2000005], lazy[2000005];
string s, s1, s2;
void prop(ll pos){
st[pos * 2] += lazy[pos];
st[pos * 2 + 1] += lazy[pos];
lazy[pos * 2] += lazy[pos];
lazy[pos * 2 + 1] += lazy[pos];
lazy[pos] = 0;
}
void update(ll l, ll r, ll L, ll R, ll pos, ll val){
if(l > R || r < L) return;
if(L <= l && r <= R){
st[pos] += val;
lazy[pos] += val;
return;
}
prop(pos);
ll mid = (l + r) / 2;
update(l, mid, L, R, pos * 2, val);
update(mid + 1, r, L, R, pos * 2 + 1, val);
st[pos] = max(st[pos * 2], st[pos * 2 + 1]);
}
void update2(ll l, ll r, ll idx, ll pos, ll val){
if(l == r){
st[pos] += val;
return;
}
prop(pos);
ll mid = (l + r) / 2;
if(idx <= mid) update2(l, mid, idx, pos * 2, val);
else update2(mid + 1, r, idx, pos * 2 + 1, val);
st[pos] = max(st[pos * 2], st[pos * 2 + 1]);
}
ll query(ll l, ll r, ll L, ll R, ll pos){
if(l > R || r < L) return -INF;
if(L <= l && r <= R) return st[pos];
prop(pos);
ll mid = (l + r) / 2;
return max(query(l, mid, L, R, pos * 2), query(mid + 1, r, L, R, pos * 2 + 1));
}
int main(){
hitaf
int T = 1;
// cin >> T;
while(T--){
cin >> n;
for(int i = 1; i <= n; i++) cin >> a[i] >> b[i];
vector<ll> ord(n + 1);
iota(ord.begin(), ord.end(), 0);
sort(ord.begin() + 1, ord.end(), [&](ll x, ll y){
return a[x] < a[y];
});
ll ans = -INF;
for(int i = 1; i <= n; i++){
ll x = ord[i];
update(1, n, 1, i, 1, b[x] - a[x]);
update2(1, n, i, 1, a[x]);
ans = max(ans, query(1, n, 1, i, 1));
update(1, n, 1, i, 1, a[x]);
}
cout << ans << endl;
}
return 0;
}
/*
dp[i][j] =
*/
