//Huyduocdithitp
#include <bits/stdc++.h>
typedef long long ll;
#define fi first
#define se second
#define pii pair<ll,ll>
#define TASK "mroads"
#define start if(fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin);freopen(TASK".out","w",stdout);}
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);
#define N 500006
using namespace std;
bool ghuy4g;
ll n, a[N], b[N], pf[N];
vector<ll> nenSo;
void solve() {
ll ans = 0;
ll mini = 0;
mini = min(mini, pf[0] - nenSo[0]);
for (int i = 1; i <= nenSo.size(); i ++) {
ans = max(ans, pf[i] - nenSo[i - 1] - mini);
if (i < nenSo.size()) {
mini = min(mini, pf[i] - nenSo[i]);
}
}
cout << ans;
}
bool klinh;
signed main(void) {
faster;
cin >> n;
for (int i = 1; i <= n; i ++) {
cin >> a[i] >> b[i];
nenSo.push_back(a[i]);
}
sort(nenSo.begin(), nenSo.end());
nenSo.resize(unique(nenSo.begin(), nenSo.end()) - nenSo.begin());
for (int i = 1; i <= n; i ++) {
a[i] = lower_bound(nenSo.begin(), nenSo.end(), a[i]) - nenSo.begin() + 1;
pf[a[i]] += b[i];
}
for (int i = 1; i <= nenSo.size(); i ++) {
pf[i] += pf[i - 1];
}
solve();
cerr << fabs(&ghuy4g - &ghuy4g) / 1048576.0;
return 0;
}
