#include<bits/stdc++.h>
#define STIZE(x) fprintf(stderr, "STIZE%d\n", x);
#define PRINT(x) fprintf(stderr, "%s = %d\n", #x, x);
#define NL(x) printf("%c", " \n"[(x)]);
#define lld long long
#define pii pair<int,int>
#define pb push_back
#define fi first
#define se second
#define mid (l+r)/2
#define endl '\n'
#define all(a) begin(a),end(a)
#define sz(a) int((a).size())
#define LINF 1000000000000000LL
#define INF 1000000000
#define EPS 1e-9
using namespace std;
#define MAXN 500010
pair<lld, lld> p[MAXN];
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); cerr.tie(0);
int N; cin >> N;
for(int i = 1; i <= N; i++) cin >> p[i].fi >> p[i].se;
sort(p+1, p+1+N);
lld sum = 0;
lld maxx = -LINF;
lld rez = -LINF;
for(int i = 1; i <= N; i++) {
maxx = max(maxx, p[i].fi - sum);
sum += p[i].se;
rez = max(rez, maxx + sum - p[i].fi);
}
cout << rez;
}
