#include <bits/stdc++.h>
#define sts(v) stable_sort(v.BE, v.E)
#define Rsts(v) stable_sort(v.rBE, v.rE)
#define rev(v) reverse(v.BE, v.E)
#define BE begin()
#define rBE rbegin()
#define E end()
#define rE rend()
#define pb push_back
#define ppb pop_back()
#define pf push_front
#define ppf pop_front()
#define F first
#define S second
using namespace std;
using ll = long long;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
vector<pair<ll, ll>> v(n + 1);
for(int i = 1; i <= n; i++){
ll a, b; cin >> a >> b;
v[i] = {a, b};
//a -> size b -> val
}
sts(v);
int pos = 0;
ll res = 0, ans[n + 1];
ans[0] = 0;
for(int i = 1; i <= n; i++){
ll a = v[i].S, b = ans[pos] - v[i].F + v[i].S;
ans[i] = max(a, b);
res = max(res, ans[i]);
ans[i] += v[i].F;
if(ans[i] > ans[pos])pos = i;
}
cout << res << '\n';
return 0;
}
