#include <bits/stdc++.h>
#define mod 1000000007
#define pb push_back
#define mid(l, r) ((l)+(r))/2
#define len(a) (a).length()
#define sz(a) (a).size()
#define xx first
#define yy second
#define inf int(2e9)
#define ff(i, a, b) for(int (i) = (a); (i) <= (b); ++(i))
#define fb(i, a, b) for(int (i) = (a); (i) >= (b); --(i))
#define maxn 500005
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pii;
template<class T>
void print(const T niz[], const int siz)
{
for(int i=0;i<siz;i++)
cout << niz[i] << " ";
cout << endl;
}
int n;
pii niz[maxn];
ll sol = -1e9;
ll mini;
bool cmp(pii a, pii b){
return a.yy < b.yy;
}
int main()
{
ios_base::sync_with_stdio(false);
cin >> n;
ff(i,1,n){
ll a, b;
cin >> a >> b;
niz[i] = {b,a};
}
sort(niz + 1, niz + n + 1,cmp);
mini = -niz[1].yy;
ll sum = 0;
ff(i,1,n){
sum += niz[i].xx;
sol = max(sol, sum - mini - niz[i].yy);
mini = min(mini, sum - niz[i+1].yy);
}
cout << sol << endl;
return 0;
}
