#pragma GCC optimize("O3")
#pragma GCC target("avx2")
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <time.h>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <bits/stdc++.h>
#define speed ios_base::sync_with_stdio(0), cin.tie(0)
#define TxtIO freopen("points.in","r",stdin); freopen("points.out","w",stdout);
using namespace std;
const int mod = 998244353;
#define ll long long
const int N=2e5+5;
//mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll binpow (ll a, ll n) {
ll res = 1;
while (n) {
if (n & 1)
res = res * a;
a = a * a;
n >>= 1;
}
return res;
}
void fcn(){
ll n;
cin>>n;
pair <ll,ll> a[n+3];
ll dp[n+3],dp2[n+3];
dp[0]=0;
for (int i=1; i<=n; i++){
cin>>a[i].first>>a[i].second;
}
sort(a+1,a+1+n);
for (int i=1; i<=n; i++){
dp[i]=dp[i-1]+a[i].second;
}
dp2[0]=-1e18;
ll ans=0;
for (int i=1; i<=n; i++){
dp2[i]=max(dp2[i-1],a[i].first-dp[i-1]);
}
for (int i=n; i>0; i--){
ans=max(ans,dp[i]+dp2[i]-a[i].first);
}
cout<<ans;
}
int main(){
//srand(time(0));
//fflush(stdout);
// freopen("bridges.in","r",stdin); freopen("bridges.out","w",stdout);
// speed;
ll T=1;
// cin>>T;
for (int i=1; i<=T; i++){
fcn();
}
}
/*
1
2 3
4 5
6 7
*/
