#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define lli long long int
#define rep(i,a,b) for(lli i = (a); i <= (b); ++i)
#define repa(i,a,b) for(lli i = (a); i >= (b); --i)
#define nl "\n"
#define MAX 500000
#define tam first
#define belleza second
lli n, res, s;
pair<lli, lli> arbol[MAX + 2];
lli acu[MAX + 2], maximo[MAX + 2];
int main()
{
cin >> n;
rep(i, 1, n) cin >> arbol[i].tam >> arbol[i].belleza;
sort(arbol + 1, arbol + 1 + n);
rep(i, 1, n) acu[i] = arbol[i].belleza + acu[i - 1];
repa(i, n, 1) maximo[i] = max(maximo[i + 1], acu[i] - arbol[i].tam);
rep(a, 1, n){
s = arbol[a].tam - acu[a - 1];
res = max(res, maximo[a] + s);
}
cout << res << nl;
return 0;
}
