#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
const int MAXN = 5e5 + 5;
int n;
pii a[MAXN];
int dp[MAXN];
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> a[i].first >> a[i].second;
}
sort(a + 1, a + n + 1);
int maxx = 0;
for (int i = 1; i <= n; i++)
{
dp[i] = max(a[i].second, maxx - a[i].first + a[i].second);
maxx = max(maxx, dp[i] + a[i].first);
}
int res = -1;
for (int i = 1; i <= n; i++)
{
res = max(res, dp[i]);
}
cout << res;
}
