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

int main(){
  int n; cin>>n;
  vector<int64_t> v(n); for (auto &i: v) cin>>i;

  int64_t cost=0,best=INT64_MAX;
  for (int i=n; i-->1;)
    cost=max(cost,v[i]-v[i-1]);
  for (int i=n; i-->2;)
    best=min(best,v[i]-v[i-2]);

  cout<<max(best,cost)<<endl;
}