#include <bits/stdc++.h>
using namespace std;

using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using LL = long long;
using VL = vector<LL>;
using VVL = vector<VL>;
using PLL = pair<LL, LL>;
using VS = vector<string>;

#define ALL(a)  begin((a)),end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

#define FF first
#define SS second
template<class S, class T>
istream& operator>>(istream& is, pair<S,T>& p){
  return is >> p.FF >> p.SS;
}
template<class S, class T>
ostream& operator<<(ostream& os, const pair<S,T>& p){
  return os << p.FF << " " << p.SS;
}
template<class T>
void maxi(T& x, T y){
  if(x < y) x = y;
}
template<class T>
void mini(T& x, T y){
  if(x > y) x = y;
}


const double EPS = 1e-10;
const double PI  = acos(-1.0);
const LL MOD = 1e9+7;

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  LL N;
  cin >> N;
  VL xs(N), ps(N);
  REP(i,N){
	cin >> xs[i] >> ps[i];
  }
  VL acc(N+1);
  REP(i,N) acc[i+1] = acc[i] + ps[i];
  VL B(N);
  REP(i,N) B[i] = acc[i+1] - xs[i];

  VL mxr(N);
  mxr[N-1] = B[N-1];
  for(int i=N-2;i>=0;--i){
	mxr[i] = max(B[i], mxr[i+1]);
  }

  LL lb = 0, ub = 1e15;
  while(ub-lb>1){
	LL L = (lb + ub) / 2;
	bool ok = false;
	REP(l,N){
	  if(mxr[l] >= L - xs[l] + acc[l]){
		ok = true;
		break;
	  }
	}
	if(ok) lb = L;
	else ub = L;
  }
  cout << lb << endl;

  return 0;
}
