#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize ("O2")
#pragma GCC optimize ("unroll-loops")
#define ll long long
#define pii pair<ll,ll>
#define fi first
#define sec second
#define ld long double
ostream& operator << (ostream& os, pii x){
os << "[";
os << " " << x.fi << " " << x.sec;
os << " ]";
return os;
}
ostream& operator << (ostream& os, pair<pii, ll> x){
os << "[";
os << " " << x.fi << " " << x.sec;
os << " ]";
return os;
}
ostream& operator << (ostream& os, pair<ll, pii> x){
os << "[";
os << " " << x.fi << " " << x.sec;
os << " ]";
return os;
}
template <typename T>
ostream& operator << (ostream& os, vector<T>tmp){
os << "[";
for(auto x : tmp) os << " " << x;
os << " ]";
return os;
}
template <typename T>
ostream& operator << (ostream& os, set<T>tmp){
os << "[";
for(auto x : tmp) os << " " << x;
os << " ]";
return os;
}
template <typename T>
ostream& operator << (ostream& os, multiset<T>tmp){
os << "[";
for(auto x : tmp) os << " " << x;
os << " ]";
return os;
}
const ll MOD = 998244353;
const ll N = 4e5;
const ll INF = 2e18;
// modulo operations
void add(ll &a, ll b) { a = (a + b) % MOD; }
void sub(ll &a, ll b) { a -= b; while(a < 0) a += MOD; a %= MOD; }
void mul(ll &a, ll b) { a = (a * b) % MOD; }
ll expo(ll a, ll b) {
ll ans = 1;
while(b > 0){
if(b & 1) mul(ans, a);
mul(a, a);
b /= 2;
}
return ans;
}
int32_t main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
for(;tc--;){
ll n; cin >> n;
vector<pii> items(n + 5);
for(int i = 1; i <= n; i++){
cin >> items[i].fi >> items[i].sec;
}
sort(items.begin() + 1, items.begin() + 1 + n);
vector<ll> ps(n + 5);
for(int i = 1; i <= n; i++) ps[i] = ps[i - 1] + items[i].sec;
ll mx = 0, ans = 0;
for(int i = 1; i <= n; i++){
mx = max(mx, -ps[i - 1] + items[i].fi);
ans = max(ans, ps[i] - items[i].fi + mx);
}
cout << ans << "\n";
}
}
/*
*/
