#include <bits/stdc++.h>
#define rep(a,b,c) for(auto a = (b); a != (c); a++)
#define repD(a,b,c) for(auto a = (b); a != (c); a--)
#define repIn(a, b) for(auto& a : (b))
#define repIn2(a, b, c) for(auto& [a, b] : (c))
constexpr bool dbg = 0;
#define DEBUG if constexpr(dbg)
#define DC DEBUG std::cerr
#define eol std::endl
#define ll long long
#define pb push_back
using namespace std;
int main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
int n;
cin >> n;
map<ll, ll> mappy, prefSum, maxSuf;
rep(i, 0, n) {
ll x, y;
cin >> x >> y;
mappy[x] += y;
}
ll prv = 0;
repIn2(k, v, mappy) prv += v, prefSum[k] = prv;
prv = -5e18;
rep(it, mappy.rbegin(), mappy.rend()) {
auto k = it -> first;
prv = max(prv, prefSum[k] - k);
maxSuf[k] = prv;
DC << "maxSuf[" << k << "] = " << prv << eol;
}
ll ans = -5e18;
prv = 0;
repIn2(k, v, mappy) {
DC << ' ' << k << ' ' << prv + k + maxSuf[k] << eol;
ans = max(ans, prv + k + maxSuf[k]);
prv = -prefSum[k];
}
cout << ans << '\n';
}
