#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>
#include <set>
#include <stack>
#include <iomanip>
#include <bitset>
#include <map>
#include <cassert>
#include <array>
#include <queue>
#include <cstring>
#include <random>
#include <unordered_set>
#include <unordered_map>
#define pqueue priority_queue
#define pb(x) push_back(x)
// #define endl '\n'
#define all(x) x.begin(), x.end()
#define int long long
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef vector<int> vi;
typedef vector<vector<int> > vvi;
// typedef tuple<ll, ll, ll> tiii;
typedef pair<int, int> pii;
typedef vector<pair<int, int> > vpii;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<char> vc;
const int inf = 1e9 + 228;
const int infll = 1e18;
const ll mod = 1e9 + 7;
const ll mod2 = 998244353;
const ld eps = 1e-14;
void fast_io(){
ios_base::sync_with_stdio(0);
cin.tie(0);
// freopen("a.in", "r", stdin);
// freopen("outputik.txt", "w", stdout);
}
void solve(){
int n;
cin >> n;
vpii kek(n);
for(int i=0; i<n; i++){
cin >> kek[i].first >> kek[i].second;
}
sort(all(kek));
for(int i=1; i<n; i++){
kek[i].second += kek[i-1].second;
}
int mn = 0;
int ans = -infll;
for(int i=0; i<n; i++){
if(i)
mn = min(mn, kek[i-1].second - kek[i].first);
else
mn = -kek[i].first;
ans = max(kek[i].second - kek[i].first - mn, ans);
}
cout << ans << endl;
}
signed main(){
fast_io();
// ;(time(NULL));
cout << fixed << setprecision(10);
int q = 1;
// cin >> q;
while(q--)
solve();
}
