#include<bits/stdc++.h>
using namespace std;
#define fast ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define int long long
#define fi first
#define se second
#define FILE "TASK"
const int N = 5e5+3;
pair<int, int> f[N];
void solve()
{
f[0]={0,0};
int n, ans, Max;
ans=Max=LLONG_MIN;
cin>>n;
for(int i=1; i<=n; i++) cin>>f[i].fi>>f[i].se;
sort(f+1, f+1+n);
for(int i=1; i<=n; i++)
{
Max = max(Max, f[i].fi - f[i-1].se);
f[i].se += f[i-1].se;
ans = max(ans, f[i].se - f[i].fi + Max);
}
cout<<ans;
}
signed main()
{
fast
solve();
return 0;
}
