# pragma GCC optimize ("O3")
# pragma GCC optimize ("Ofast")
# pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
#define MEM 555555
#define sanic ios_base::sync_with_stdio(0)
#define x first
#define y second
#define pf push_front
#define pb push_back
#define all(v) v.begin(), v.end()
#define sz size()
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pi;
typedef pair<pi, pi> pii;
typedef pair<double, ll> pir;
const ll MOD = 1e9+7;
const ll INF = 2e14+7;
ll mul(ll a, ll b){
return ((a*b)%MOD+MOD)%MOD;
}
ll add(ll a, ll b){
return ((a+b)%MOD+MOD)%MOD;
}
ll t,n,ans;
vector<ll> vv, o;
pi a[MEM];
ll p[MEM];
signed main(){
sanic; cin.tie(0); cout.tie(0);
cin >> n;
for(int i=0; i<n; i++)
cin >> a[i].x >> a[i].y;
sort(a,a+n);
p[0] = a[0].y;
for(int i=1; i<n; i++)
p[i] = p[i-1]+a[i].y;
ll ans=0;
ll mn=a[0].x;
for(int i=0; i<n; i++){
ans = max(p[i]-a[i].x+mn, ans);
mn = max(mn, a[i+1].x-p[i]);
}
cout << ans;
}
/*
5 15
0 2 2 3 3
2 0 3 3 2
2 3 0 2 3
3 3 2 0 2
3 2 3 2 0
*/
