#include <iostream>
#include <algorithm>
#include <climits>
using namespace std;
struct ceva {
long long sz, val;
} v[500002];
bool cmp(ceva x, ceva y) {
return x.sz < y.sz;
}
long long n;
long long sp[500002], tree[2000005];
void build(long long node, long long st, long long dr) {
if (st == dr) {
tree[node] = sp[st] - v[st].sz;
return ;
}
long long mij = (st + dr)/2;
build(2*node, st, mij);
build(2*node+1, mij+1, dr);
tree[node] = max(tree[2*node], tree[2*node+1]);
}
long long query(long long node, long long st, long long dr, long long left, long long right) {
if (left <= st and dr <= right) {
return tree[node];
}
long long mij = (st + dr)/2;
long long ans1 = LLONG_MIN, ans2 = LLONG_MIN;
if (left <= mij)
ans1 = query(2*node, st, mij, left, right);
if (mij < right)
ans2 = query(2*node+1, mij+1, dr, left, right);
return max(ans1, ans2);
}
signed main()
{
cin >> n;
for (long long i = 1; i <= n; i++) {
cin >> v[i].sz >> v[i].val;
}
sort(v+1, v+n+1, cmp);
for (long long i = 1; i <= n; i++) {
sp[i] = sp[i-1] + v[i].val;
}
build(1, 1, n);
long long maxim = LLONG_MIN;
for (long long i = 1; i <= n; i++) {
long long x = sp[i-1] - v[i].sz;
long long rezdr = query(1, 1, n, i, n);
maxim = max(maxim, rezdr-x);
}
cout << maxim;
return 0;
}
