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

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0); 
    int N;cin>>N;
    vector<int> A(2*N+1, 0);
    for(int i=0;i<N;++i) cin>>A[i];
    int sum=accumulate(A.begin(),A.end(),0);
    int ans=1e9;
    for(int i=1;i<=N&&i*i<=sum;++i){
        vector<int> B(2*N+1,0);
        for(int j=0;j<i;++j){
            B[j]=j+1;
            B[2*i-2-j]=j+1;
        }
        int surplus=0, deficit=0;
        for(int i=0;i<=2*N;++i){
            surplus+=max(0,A[i]-B[i]);
            deficit+=max(0,B[i]-A[i]);
        }
        ans=min(ans,max(surplus,deficit));
    }
    cout<<ans<<endl;
    return 0;
}