#include <bits/stdc++.h>
#define int long long
#define bp __builtin_popcountll
#define pb push_back
#define in(s) freopen(s, "r", stdin);
#define out(s) freopen(s, "w", stdout);
#define inout(s, end1, end2) freopen((string(s) + "." + end1).c_str(), "r", stdin),\
freopen((string(s) + "." + end2).c_str(), "w", stdout);
#define fi first
#define se second
#define bw(i, r, l) for (int i = r - 1; i >= l; i--)
#define fw(i, l, r) for (int i = l; i < r; i++)
#define fa(i, x) for (auto i: x)
using namespace std;
const int mod = 1e9 + 7, inf = 1061109567;
const long long infll = 4557430888798830399;
const int N = 5e5 + 5;
struct Painting {
int size, val;
bool operator<(const Painting &rhs) {
return size < rhs.size;
}
} p[N];
int n;
signed main() {
#ifdef BLU
in("blu.inp");
#endif
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n;
fw (i, 0, n) cin >> p[i].size >> p[i].val;
sort(p, p + n);
fw (i, 1, n) p[i].val += p[i - 1].val;
int ans = -infll, curMx = -infll;
fw (i, 0, n) {
curMx = max(curMx, p[i].size - (i ? p[i - 1].val : 0));
ans = max(ans, p[i].val - p[i].size + curMx);
}
cout << ans;
return 0;
}
