#include <bits/stdc++.h>
#define GOOD_LUCK ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define int long long
#define endl "\n"
#define ff first
#define ss second
#define pb push_back
#define all(v) v.begin(), v.end()
using namespace std;
constexpr int MAX = 2e+5 + 1, INF = 2e+16, MOD = 1e+9 + 7, K = 31;
void _() {
int n;
cin >> n;
vector <pair<int, int>> v(n);
int ma=0;
for (auto &i : v) cin >> i.ff >> i.ss, ma = max(ma, i.ss);
sort(all(v));
int sum=0, res=0;
int j = 0;
for (int i = 0; i < n; i++) {
sum += v[i].ss;
res = max(res, sum - v[i].ff + v[j].ff);
if (v[i].ff + v[i].ss > sum + v[j].ff) {
j = i;
sum = v[i].ss;
}
}
cout << max(res, ma);
}
signed main() {
GOOD_LUCK
int tests=1;
// cin >> tests;
for (int i=1; i <= tests; i++) {
_();
cout << endl;
}
return 0;
}
