#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define p(x,y) pair<ll,ll>(x,y)
#define BIT(i,x) ((x>>i)&1)
#define MASK(x) (1<<x)
#define ld long double
#define __builtin_popcount __builtin_popcountll
#define pll pair<ll,ll>
template<class T1,class T2>
bool maximize(T1 &x,const T2 &y)
{
if(x<y)
{
x=y;
return 1;
}
return 0;
}
template<class T1,class T2>
bool minimize(T1 &x,const T2 &y)
{
if(x>y)
{
x=y;
return 1;
}
return 0;
}
void online()
{
std::ios_base::sync_with_stdio(0);
cin.tie(0);
}
const ll M=1e16;
struct SegmentTree
{
vector<ll> Tree;
ll n;
SegmentTree(ll _n=0)
{
n=_n;
Tree.resize(4*n+1);
}
ll update(ll i,ll l,ll r,ll pos,ll vl)
{
if(r<pos||pos<l) return Tree[i];
if(l==r) return Tree[i]=vl;
return Tree[i]=min(update(i*2,l,(l+r)/2,pos,vl),update(i*2+1,(l+r)/2+1,r,pos,vl));
}
ll query(ll i,ll l,ll r,ll u,ll v)
{
if(v<l||r<u) return M;
if(u<=l&&r<=v) return Tree[i];
return min(query(i*2,l,(l+r)/2,u,v),query(i*2+1,(l+r)/2+1,r,u,v));
}
};
const ll N=5e5+10;
ll n,f[N];
pll a[N];
int main()
{
online();
cin>>n;
SegmentTree S(n);
for(int i=1;i<=n;i++)
{
cin>>a[i].fi>>a[i].se;
}
sort(a+1,a+n+1);
ll ans=0;
for(int i=1;i<=n;i++)
{
a[i].se+=a[i-1].se;
S.update(1,1,n,i,a[i-1].se-a[i].fi);
f[i]=a[i].se-a[i].fi+a[1].fi;
maximize(f[i],a[i].se-a[i].fi-S.query(1,1,n,1,i));
maximize(ans,f[i]);
}
cout<<ans;
}
