#include <iostream>
#include <algorithm>
#define MAX_N 500000
#define xx first
#define yy second
using namespace std;
typedef long long lint;
const lint sqrInf = (lint)(1e18) - 1;
int n;
pair <lint, lint> v[MAX_N + 1];
lint rez;
lint s[MAX_N + 1];
void readFile()
{
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n;
for(int i = 1; i <= n; i ++)
cin >> v[i].xx >> v[i].yy;
}
void solve()
{
sort(v + 1, v + n + 1);
lint mx = -sqrInf;
for(int i = 1; i <= n; i ++)
{
rez = max(rez, v[i].yy);
s[i] = s[i - 1] + v[i].yy;
rez = max(rez, mx - v[i].xx + s[i]);
mx = max(mx, v[i].xx - s[i - 1]);
}
}
void printFile()
{
cout << rez << "\n";
}
int main()
{
readFile();
solve();
printFile();
return 0;
}
