#include <bits/stdc++.h>
using namespace std;
//macros
typedef long long ll;
typedef pair<int, int> ii;
typedef pair<ll, ll> lll;
typedef tuple<int, int, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
typedef vector<lll> vlll;
#define REP(a,b,c) for(int a=int(b); a<int(c); a++)
#define RE(a,c) REP(a,0,c)
#define RE1(a,c) REP(a,1,c+1)
#define REI(a,b,c) REP(a,b,c+1)
#define REV(a,b,c) for(int a=int(c-1); a>=int(b); a--)
#define INF 1e9
#define pb push_back
#define fi first
#define se second
#define sz size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//===================//
// Added libraries //
//===================//
//===================//
//end added libraries//
//===================//
void program();
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
program();
}
//===================//
// begin program //
//===================//
const int MX = 7e5;
ll n, a[MX], b[MX];
ll SA[MX];
ll sm[MX];
void program() {
cin>>n;
RE(i,n) cin>>a[i]>>b[i];
RE(i,n) SA[i]=i;
sort(SA,SA+n, [](int i, int j) {
return a[i]<a[j];
});
sm[0] = 0;
RE(i,n) sm[i+1] = sm[i]+b[SA[i]];
ll ans = 0;
ll mx = a[SA[0]]-sm[0];
RE(i,n) {
mx = max(mx, a[SA[i]]-sm[i]);
ans = max(ans, sm[i+1]-a[SA[i]]+mx);
}
cout<<ans<<endl;
}
