#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define MP make_pair
#define PB push_back
using ll = long long;
using ld = long double;
using pi = pair<int, int>;
using pll = pair<ll, ll>;
template<typename T>
using vec = vector<T>;
template<typename T, int N>
using arr = array<T, N>;
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
const int INF = 1e9 + 7;
const int MOD = 998244353;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N;
cin >> N;
vec<pair<ll, ll>> A(N + 1);
for (int i = 1; i <= N; i++)
cin >> A[i].F >> A[i].S;
sort(A.begin() + 1, A.end());
A[0] = A[1];
ll l = 1, ans = 0, sum = 0, diff = 0;
for (int r = 1; r <= N; r++)
{
sum += A[r].S;
diff += A[r].F - A[r - 1].F;
while (l < r && A[l + 1].F - A[l].F > A[l].S)
{
l++;
sum -= A[l].S;
diff -= A[l + 1].F - A[l].F;
}
ans = max(ans, sum - diff);
}
cout << ans << '\n';
}
