// In the name of Allah. Ya ali!
#include<bits/stdc++.h>
#define double long double
typedef long long ll;
const ll MAX_N = 1.2e6+10;
const ll MOD = 1e9+7;
using namespace std;
ll mx[MAX_N];
ll fl[MAX_N];
pair<ll,ll> lr[MAX_N];
int n,y;
void shift(int k)
{
int l = k*2;
int r = k*2+1;
fl[l] += fl[k];
fl[r] += fl[k];
mx[l] += fl[k];
mx[r] += fl[k];
fl[k] = 0;
}
void update(int k)
{
mx[k] = max(mx[k*2],mx[k*2+1]);
}
void add(int l,int r,int a,int b,int k,ll x)
{
if (r<a or b<l)
return;
if (a<=l and r<=b)
{
fl[k] += x;
mx[k] += x;
return;
}
int mid = (l+r)/2;
shift(k);
add(l,mid,a,b,k*2,x);
add(mid+1,r,a,b,k*2+1,x);
update(k);
}
int main()
{
cin >> n;
y = (1<<((int)ceil(log2(n))));
ll ans = 0;
for(int i = 0;i<n;++i)
scanf("%lld%lld",&lr[i].first,&lr[i].second),ans = max(ans,lr[i].second);
sort(lr,lr+n);
add(0,y-1,0,0,1,lr[0].second);
for(int i = 1;i<n;++i)
{
add(0,y-1,0,i-1,1,-lr[i].first+lr[i-1].first+lr[i].second);
add(0,y-1,i,i,1,max(lr[i].second,mx[1]));
ans = max(ans,mx[1]);
}
cout << ans;
return 0;
}
