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

typedef long long ll ;

const int N = 1e6 + 4;


int n;

ll a[N] ;

ll b[N];


bool can(int x)
{
    deque<pair<int ,int > > aa , bb;

    for (int i = 0; i < n; ++i) {

        aa.push_front({i , a[i]}) ;

        bb.push_front({i , b[i]}) ;

        while ( bb.back().first + x < aa.back().first  )
        {
            bb.pop_back() ;
        }

        if(aa.back().first + x < bb.back().first) return 0;

        while ( !bb.empty() && !aa.empty()  )
        {
            auto p = bb.back() ;
            bb.pop_back();

            auto p2 = aa.back() ;
            aa.pop_back() ;

            int mn = min(p.second , p2.second );

            p.second -= mn;
            p2.second -= mn ;

            if(p.second) bb.push_back(p) ;
            if(p2.second) aa.push_back(p2) ;
        }
    }

    return aa.empty() ;
}

int main() {
    cin.tie(0);cin.sync_with_stdio(0);
    cout.tie(0);cout.sync_with_stdio(0);

    cin >> n;

    for (int i = 0; i < n; ++i) {
        cin >> a[i] ;
    }
    for (int i = 0; i < n; ++i) {
        cin >> b[i] ;
    }

    int l = 0 , r = n-1 , md , ans = -1 ;

    while (l <= r)
    {
        md=(l + r) /2 ;

        if(can(md)) ans = md , r= md-1 ;
        else l = md+1;
    }

    cout << ans ;
}