//Suleyman Atayew
#include <algorithm>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <vector>
#include <bitset>
#include <queue>
#include <cmath>
#include <map>
#include <set>
#define N 200010
#define ff first
#define ss second
#define pb push_back
#define ll long long
#define mod 1000000007
#define pii pair <ll, ll>
#define sz(a) (ll)(a.size())
ll bigmod(ll a, ll b) { if(b==0)return 1; ll ret = bigmod(a, b/2); return ret * ret % mod * (b%2 ? a : 1) % mod; }
using namespace std;
ll n;
pii p[N];
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n;
ll sum = 0, ans = 0;
for(ll i = 1; i <= n; i++) {
cin >> p[i].ff >> p[i].ss;
ans = max(ans, p[i].ss);
}
sort(p+1, p+n+1);
queue <ll> Q;
for(ll i = 1; i <= n; i++) {
sum = sum + p[i].ss - (i != 1 ? p[i].ff - p[i-1].ff : 0);
ans = max(ans, sum);
while(!Q.empty() && sum < 0) {
ll x = Q.front();
sum = sum - p[x].ss - (p[x+1].ff - p[x].ff);
Q.pop();
}
Q.push(i);
ans = max(ans, sum);
}
cout << ans;
}
