#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(998244353)
using namespace std;
template<class T1, class T2>
bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2>
bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2>
void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}
template<class T1, class T2>
void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}
template<class T>
void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}
const int MAX = 5e5 + 10;
int N;
pair<ll, ll> arts[MAX];
ll suf[MAX];
void solve(){
cin >> N;
for(int i = 1; i <= N; i++){
cin >> arts[i].fi >> arts[i].se;
}
sort(arts + 1, arts + N + 1);
ll ans = -oo;
for(int i = 1; i <= N; i++){
maximize(ans, arts[i].se);
}
for(int i = N; i > 1; i--){
suf[i] = suf[i + 1] + arts[i].se - arts[i].fi + arts[i - 1].fi;
}
ll minVal = 0;
for(int i = N - 1; i >= 1; i--){
maximize(ans, suf[i + 1] - minVal + arts[i].se);
minimize(minVal, suf[i + 1]);
}
cout << ans << '\n';
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
solve();
return 0;
}
