#include <bits/stdc++.h>
#define sz size()
#define FOR(x, n, m, d) for(int x = n; x <= m; x += d)
#define all(v) v.begin(), v.end()
#define S second
#define F first
#define nikita ios_base::sync_with_stdio(0), cin.tie(0);
#define pb push_back
#define int long long
using namespace std;
const int N = 5e5+5;
int a[N], b[N], c[N], n, l, ans, k;
signed main(){
nikita
cin >> n;
vector<pair<int, int>>v;
set<int>st;
map<int, int>mp;
FOR(i, 1, n, 1){
cin >> a[i] >> b[i];
st.insert(a[i]);
mp[a[i]] += b[i];
}
for(auto i : st)v.pb({i, mp[i]});
sort(all(v));
ans = 0;
int lst = 0;
k = 1;
l = 0;
int cnt = 0;
int po = 0;
for(auto i : v){
ans -= (i.F - lst);
ans += i.S;
c[k] += c[k-1] + i.S;
if(i.F - l - c[k-1] + po >= 0)ans += i.F - l - c[k-1] + po, l = i.F, po = c[k-1];
k ++;
lst = i.F;
cnt = max(cnt, ans);
}
cout << cnt;
}
