#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <set>
#include <iterator>
#include <stack>
#include <map>
#include <math.h>
#include <bitset>
#include <deque>
#include <string>
#include <tuple>
#include <queue>
#include <numeric>
#include <unordered_set>
#include <unordered_map>
#define pi 3.141592653589793238
#define ll long long
#define ld long double
#define rep(i, a, b) for (long long i = a; i <= b; i++)
#define mod 998244353ll
#define INF 1000000000000000000
#define pb push_back
#define ff first
#define ss second
#define endl '\n'
#define all(x) (x).begin (), (x).end ()
#define sz(x) (ll) (x).size ()
#define reunique(v) v.resize(std::unique(v.begin(), v.end()) - v.begin())
#define rank rnk
#define log lg
#define fast \
ios_base::sync_with_stdio (false); \
cin.tie (NULL); \
cout.tie (NULL)
using namespace std;
signed main()
{
fast;
// freopen("milkorder.in","r",stdin);
// freopen("milkorder.out","w",stdout);
ll n;
cin>>n;
pair <ll,ll> p[n+1];
rep(i,1,n)
cin>>p[i].ff>>p[i].ss;
sort(p+1,p+n+1);
ll csum[n+1];
csum[0]=0;
rep(i,1,n)
csum[i]=csum[i-1]+p[i].ss;
ll val[n+1];
val[0]=0;
rep(i,1,n)
val[i]=csum[i]-p[i].ff;
ll mx[n+1];
mx[n]=val[n];
for(ll i=n-1;i>=1;--i)
mx[i]=max(mx[i+1],val[i]);
ll ans=-INF;
rep(i,1,n)
ans=max(ans,mx[i]-(csum[i-1]-p[i].ff));
cout<<ans;
return 0;
}
