#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define maxn 200005
int n;
struct varid{
ll a; //kich thuoc
ll b; //gia tri
};
bool cmp(const varid& x, const varid& y){
return x.a < y.a;
}
vector<varid> t;
vector<ll> p;
vector<ll> minn;
ll ans = LLONG_MIN;
int main()
{
cin >> n;
t.resize(n+1);
p.resize(n+1);
for (int i = 1; i <= n; i++) cin >> t[i].a >> t[i].b;
sort(t.begin()+1, t.end(), cmp); //sort theo size tang dan
p[1] = t[1].b;
for (int i = 2; i <= n; i++){
p[i] = p[i-1] + t[i].b;
}
minn[1] = -t[1].a;
for (int i = 2; i <= n; i++){
minn[i] = min(minn[i-1], p[i-1] - t[i].a);
}
for (int r = 1; r <= n; r++){
//tim min cua p[r-1]\ - a[r], r <= l
ans = max(ans, p[r] - t[r].a - minn[r]);
}
cout << ans << '\n';
return 0;
}
