#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
#define fastio ios::sync_with_stdio(false), cin.tie(0)
#define pb push_back
#define eb emplace_back
#define f first
#define s second
#define int long long
#define lowbit(x) x&-x
const int maxn = 2e5 + 5;
signed main(void){
fastio;
int n;
cin>>n;
vector<pll> a(n);
for(int i = 0; i < n; i++) cin>>a[i].f>>a[i].s;
sort(a.begin(), a.end());
int mn = 0, ttl = 0, ans = 0;
for(int i = 0; i < n; i++){
mn = min(mn, ttl - a[i].f);
ttl += a[i].s;
ans = max(ans, ttl - a[i].f - mn);
}
cout<<ans<<"\n";
}
