#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 watch(x) cout<<(#x)<<"="<<(x)<<'\n'
#define mset(d,val) memset(d,val,sizeof(d))
#define setp(x) cout<<fixed<<setprecision(x)
#define forn(i,a,b) for(int i=(a);i<(b);i++)
#define fore(i,a,b) for(int i=(a);i<=(b);i++)
#define pb push_back
#define F first
#define S second
#define pqueue priority_queue
#define fbo find_by_order
#define ook order_of_key
typedef long long ll;
typedef pair<ll,ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;
typedef long double ld;
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> pbds;
void amin(ll &a, ll b){ a=min(a,b); }
void amax(ll &a, ll b){ a=max(a,b); }
void YES(){cout<<"YES\n";} void NO(){cout<<"NO\n";}
void SD(int t=0){ cout<<"PASSED "<<t<<endl; }
const ll INF = ll(1e18);
const int MOD = 998244353;
bool DEBUG = 0;
const int MAXN = 500005;
int n;
ii a[MAXN];
ll pre[MAXN];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin>>n;
forn(i,0,n) cin>>a[i].F>>a[i].S;
sort(a,a+n);
forn(i,0,n){
pre[i]=a[i].S;
if(i>0) pre[i]+=pre[i-1];
}
ll Max=0,ans=0;
forn(i,0,n)
{
Max=max(Max, a[i].F-(i==0?0LL:pre[i-1]));
ans=max(ans, pre[i]-a[i].F+Max);
}
cout<<ans<<'\n';
return 0;
}
