#undef _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define int long long
#define pb push_back
#define fi first
#define si second
#define ar array
typedef pair<int,int> pi;
typedef tuple<int,int,int> ti;
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {cerr << " " << to_string(H);debug_out(T...);}
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
int N, ans, sum[500010], mn = (1<<30);
pi A[500010];
// S - (Amax - Amin) = Sr - Ar - (Sl-1 - Al)
signed main() {
fast;
cin >> N;
for (int i = 1; i <= N; ++i) cin >> A[i].fi >> A[i].si;
sort(A + 1, A + 1 + N);
for (int i = 1; i <= N; ++i) sum[i] = sum[i - 1] + A[i].si;
for (int i = 1; i <= N; ++i) {
if (i == 1) {
ans = A[i].si;
mn = -A[i].fi;
} else {
mn = min(mn, sum[i - 1] - A[i].fi);
ans = max(ans, sum[i] - A[i].fi - mn);
}
}
cout << ans;
return 0;
}
