//wait darn
#include<bits/stdc++.h>
using namespace std;
#define x first
#define y second
typedef long long ll;
typedef pair<ll,ll> art;
const int MAXN = 1024576;
int N;
art muse[MAXN];
ll cost[MAXN];
ll psum[MAXN];
void input() {
cin >> N;
for(int i = 0; i < N; i++) {
cin >> muse[i].x >> muse[i].y;
}
sort(muse, muse+N);
}
void process() {
cost[0] = 0;
for(int i = 1; i < N; i++) {
cost[i] = muse[i].y - (muse[i].x - muse[i-1].x);
//cout << cost[i] << endl;
}
psum[0] = 0;
for(int i = 1; i < N; i++) {psum[i] = psum[i-1]+cost[i];}
}
void solve() {
ll ans = 0;
ll curm = psum[N-1];
for(int i = N-1; i >= 0; i--) {
curm = max(curm, psum[i]);
ans = max(ans, curm-psum[i]+muse[i].y);
}
cout << ans << endl;
}
int main() {
ios_base::sync_with_stdio(false);
input();
process();
solve();
}
