#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,int>
#define X first
#define Y second
const int N=5e5+5;
int n; ll res;
pii a[N];
namespace sub1
{
void ql(int i,ll mi,ll ma,ll sum)
{
if (i>n)
{
res=max(res,sum-(ma-mi));
return;
}
ql(i+1,mi,ma,sum);
ql(i+1,min(mi,a[i].X),max(ma,a[i].X),sum+a[i].Y);
}
void solve()
{
res=0;
for (int i=1;i<=n;i++)
ql(i+1,a[i].X,a[i].X,a[i].Y);
cout << res;
}
}
namespace sub2
{
ll temp,ma,res;
void solve()
{
sort(a+1,a+n+1);
ma=a[1].Y+a[1].X;
res=a[1].Y;
for (int i=2;i<=n;i++)
{
temp=ma-a[i].X+a[i].Y;
if (temp<a[i].Y) temp=a[i].Y;
res=max(res,temp);
ma=max(ma,temp+a[i].X);
}
cout << res;
}
}
int main()
{
ios_base::sync_with_stdio(NULL);
cin.tie(NULL); cout.tie(NULL);
cin >> n;
for (int i=1;i<=n;i++)
cin >> a[i].X >> a[i].Y;
sub2::solve();
}
