#include <bits/stdc++.h> using namespace std; #define N 10000005 int lc[N]; int sj[N]; int main(){ int n,left = N,right = 0; cin>>n; for (int i = 0;i<n;i++) cin>>lc[i]; for (int i = 0;i<n;i++){ cin>>sj[i]; if (left >= lc[i] - sj[i]) left = lc[i] - sj[i]; if (right <= lc[i] + sj[i]) right = lc[i] + sj[i]; } printf("%.1f",(right + left)*1.0 / 2); return 0; }