#include <bits/stdc++.h>

using namespace std;

int n;
int a[100001];
int b[100001];
long long int res = 0;
set <int> S,S2;
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> n;
    for(int i=1;i<=n;i++) cin >> a[i];

    for(int i=1;i<=n;i++)
    {
        b[i] = a[i];
        if(a[i] >= 1) S.insert(i);
    }

    S2 = S;

    for(int i=1;i<=n;i++)
    {
        if(a[i]==0)
        {
            auto it = S.lower_bound(i);
            int Min = 1e9;
            int idx = -1;
            if(it==S.end())
            {
                it--;
                int d = abs(i - *it);
                if(Min > d)
                {
                    Min = d;
                    idx = *it;
                }                
            }
            else
            {
                int d = abs(i - *it);
                if(Min > d)
                {
                    Min = d;
                    idx = *it;
                }             
            }
            a[idx]-=1;
            a[i] += 1;
            res += Min;
            if(a[idx]==0) S.erase(idx);
        }
    }

    S = S2;
    memcpy(a,b,sizeof(b));
    long long int sum = 0;
    for(int i=n;i>=1;i--)
    {
        if(a[i]==0)
        {
            auto it = S.lower_bound(i);
            int Min = 1e9;
            int idx = -1;
            if(it==S.begin())
            {
                int d = abs(i - *it);
                if(Min > d)
                {
                    Min = d;
                    idx = *it;
                }             
            }
            else
            {
                it--;
                int d = abs(i - *it);
                if(Min > d)
                {
                    Min = d;
                    idx = *it;
                }                
            }
            a[idx]-=1;
            a[i] += 1;
            sum += Min;
            if(a[idx]==0) S.erase(idx);            
        }
    }

    res = min(res,sum);
    cout << res << '\n';

    return 0;
}