#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define vl vector<ll>
#define vi vector<int>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pb push_back
#define sz(v) (ll)(v.size())
#define f first
#define s second
#define pii pair<int, int>
#define pll pair<ll, ll>
using namespace std;
void solve()
{
ll n, i, j;
cin >> n;
vector<pll>vect;
for(i = 1; i <= n; i++)
{
ll x, y;
cin >> x >> y;
vect.pb({x, y});
}
sort(all(vect));
ll res = 0;
for(i = 0; i < 1; i++)
{
ll sm = 0;
for(j = i; j < sz(vect); j++)
{
sm += vect[j].s;
res = max(res, sm - (vect[j].f - vect[i].f));
}
}
cout << res << "\n";
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll tests = 1;
//cin >> tests;
while(tests--)
{
solve();
}
}
