#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define fbo find_by_order
#define ook order_of_key
typedef long long ll;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef long double ld;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
typedef set<int>::iterator sit;
typedef map<int,int>::iterator mit;
typedef vector<int>::iterator vit;
ll a[511111];
ll b[511111];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
int n; cin>>n;
vector<pair<ll,ll> > vec;
for(int i=0;i<n;i++)
{
ll x,y; cin>>x>>y;
vec.pb(mp(x,y));
}
sort(vec.begin(),vec.end());
for(int i=1;i<=n;i++)
{
a[i] = vec[i-1].fi;
b[i] = vec[i-1].se;
}
for(int i=1;i<=n;i++)
{
b[i]+=b[i-1];
}
ll mini = b[0] - a[1];
ll ans = 0;
for(int i=1;i<=n;i++)
{
ans = max(ans, b[i]-a[i]-mini);
if(i<n) mini=min(mini,b[i]-a[i+1]);
}
cout<<ans<<'\n';
}
