#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
#define pb push_back
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define N 500005
#define INF 0x3f3f3f3f3f3f3f3f
#define MOD 1000000007LL
vector<pair<ll, ll> > v;
ll p[N];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
for(int i = 1; i <= n; ++i){
ll a, b;
cin>>a>>b;
v.push_back({a, b});
}
v.push_back({0, 0});
sort(v.begin(), v.end());
ll mn = INF;
ll res = -INF;
for(int i = 1; i <= n; ++i){
p[i] = p[i - 1] + v[i].ss;
mn = min(mn, p[i - 1] - v[i].ff);
res = max(res, p[i] - v[i].ff - mn);
}
cout<<res;
}
