#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vii> vvii;
typedef vector<vi> vvi;
typedef pair<double, double> dodo;
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)
int N;
ll A[500000], B[500000];
ll opt[500000];
int main(int argc, char **argv) {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> N;
for (int i = 0; i < N; i++) cin >> B[i] >> A[i];
vector<pair<ll, ll> > tmp;
for (int i = 0; i < N; i++) tmp.pb(mp(B[i], A[i]));
sort(tmp.begin(), tmp.end());
for (int i = 0; i < N; i++) A[i] = tmp[i].second, B[i] = tmp[i].first;
opt[N-1] = A[N-1];
for (int i = N-2; i >= 0; i--) {
opt[i] = A[i];
ll delta = opt[i+1] - (B[i+1] - B[i]);
if (delta > 0) opt[i] += delta;
}
ll ans = 0;
for (int i = 0; i < N; i++) {
ans = max(ans, opt[i]);
}
cout << ans << endl;
return 0;
}
