#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#include "bits/stdc++.h"
using namespace std;
#define pb push_back
#define F first
#define S second
#define f(i,a,b) for(int i = a; i < b; i++)
#define endl '\n'
using ll = long long;
using db = long double;
using ii = pair<int, int>;
const int N = 2e5 + 5, LG = 19, MOD = 1e9 + 7;
const int SQ =225;
const long double EPS = 1e-7;
int32_t main(){
//#ifdef ONLINE_JUDGE
ios_base::sync_with_stdio(0);
cin.tie(0);
//#endif
int n;
cin >> n;
vector<pair<ll, ll>> v(n);
for(auto & x : v) cin >> x.F >> x.S;
sort(v.begin(),v.end());
ll mx = v[0].S, cur = v[0].S;
f(i,1,n){
cur += v[i].S;
cur -= (v[i].F - v[i-1].F);
cur = max(cur, v[i].S);
mx = max(mx, cur);
}
cout << mx << endl;
return 0;
}
