#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
#ifdef JahonaliX
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n;
cin >> n;
vector<ll> a(n), b(n);
ll s, ans = 0;
for (int i = 0; i < n; ++i) cin >> a[i] >> b[i];
vector<int> o(n);
iota(o.begin(), o.end(), 0);
sort(o.begin(), o.end(), [&] (int i, int j) {
if (a[i] == a[j]) return b[i] > b[j];
return a[i] < a[j];
});
s = a[o[0]];
for (int i : o) {
s += b[i];
s = max(s, b[i] + a[i]);
ans = max(ans, s - a[i]);
}
cout << ans;
return 0;
}
