#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define MP make_pair
#define pb push_back
#define REP(i,n) for(int (i) = 0; (i) < (n); (i)++)
void fastio() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
}
const double EPS = 0.00001;
const int INF = 1e17+500;
const int N = 1e5+5;
const int M = 3e5+5;
const int ALPH = 26;
const int LGN = 25;
const int MOD = 1e9+7;
int n,m,q;
vector<array<int,2> > arr; // sz, price
vector<int> pref;
inline void solve() {
cin>>n;
arr.resize(n);
for(int i = 0; i<n; i++) {
cin >> arr[i][0] >> arr[i][1];
}
arr.pb({0,0});
sort(arr.begin(), arr.end());
pref.resize(n+1);
pref[0] = 0;
for(int i = 1; i<=n; i++) {
pref[i] = pref[i-1] + arr[i][1];
}
int mx = -INF;
int ans = -INF;
for (int i = n; i >= 1; i--)
{
mx = max(mx, pref[i] - arr[i][0]);
ans = max(ans, mx + arr[i][0] - pref[i-1]);
}
cout<<ans<<"\n";
}
signed main() {
fastio();
int test = 1;
//cin>>test;
while(test--) {
solve();
}
}
