//#pragma GCC optimize("Ofast,unroll-loops")
//#pragma GCC target("avx,avx2,fma,lzcnt,popcnt")
#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define ii pair<int,int>
#define ill pair<ll,ll>
#define el cout<<'\n'
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define int long long
const ll mod=1e9+7;
const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
const int nmax=5e5;
void add ( int&a , int b ) { if ((a+=b) > mod ) a -= mod ; }
void sub ( int&a , int b ) { if ((a-=b) < 0 ) a += mod ; }
template<typename T> void chkmin(T& x, T y) {if(x > y) x = y;}
template<typename T> void chkmax(T& x, T y) {if(x < y) x = y;}
using namespace std;
ii a[nmax+5];
ll sum[nmax+5];
int val[nmax+5];
int pos[nmax+5];
int get(int x)
{
int p=pos[x];
// cout<<p<<" "<<;el;
return (sum[p]-sum[x-1]+a[x].fi-a[p].fi);
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
int n;
cin>>n;
for(int i=1;i<=n;i++)
cin>>a[i].fi>>a[i].se;
sort(a+1,a+1+n);
for(int i=1;i<=n;i++)
sum[i]=sum[i-1]+a[i].se;
for(int i=1;i<=n;i++)
val[i]=sum[i]-a[i].fi;
pos[n]=n;
int mi=val[n];
for(int i=n-1;i>=1;i--)
{
if(mi<val[i])
{
pos[i]=i;
mi=val[i];
}
else
pos[i]=pos[i+1];
}
int ans=0;
for(int i=1;i<=n-1;i++)
ans=max(ans,get(i));
cout<<ans;
}
