#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define cd complex<ld>
#define pll pair<ll,ll>
#define pii pair<int,int>
#define pld pair<ld,ld>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
ll n;
pll A[500005];
ll dp[500005];
ll Max[500005];
void solve()
{
cin >> n;
for(int i = 1; i<= n; i++)
{
cin >> A[i].fi >> A[i].se;
}
sort(A+1, A+n+1);
for(int i = 1; i<= n; i++) dp[i] = dp[i-1]+A[i].se;
Max[n] = dp[n]-A[n].fi;
for(int i = n-1; i>= 1; i--)
{
Max[i] = dp[i]-A[i].fi;
Max[i] = max(Max[i],Max[i+1]);
}
ll ans = LLONG_MIN;
for(int i = n; i>= 1; i--)
{
ans = max(ans, Max[i]-dp[i-1]+A[i].fi);
}
cout << ans;
}
signed main()
{
//freopen("IN.txt","r",stdin);
//freopen("OUT.txt","w",stdout);
ios_base::sync_with_stdio(NULL) ; cin.tie(nullptr) ; cout.tie(nullptr);
ll t = 1;
//cin >> t;
while(t--)
{
solve();
cout << "\n";
}
}
