#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;

#define X first
#define Y second
#define mk make_pair
#define inb push_back
#define y1 ggggggggggggg

int solve();

int main()
{
    solve();
    return 0;
}

const int BUFSZ = (int)1e6 + 7;

char buf[BUFSZ];

string get_str()
{
    scanf(" %s", buf);
    return string(buf);
}

const double INF = (double)1e9 + 7;

int solve()
{
    int n;
    scanf("%d", &n);
    vi t(n);
    for (int i = 0; i < n; ++i)
    {
        scanf("%d", &t[i]);
    }
    vector<vi> f(n, vi(n));
    for (int l = 0; l < n; ++l)
    {
        f[l][l] = 140;
        for (int r = l + 1; r < n; ++r)
        {
            f[l][r] = 140 + max(t[r] - t[l] - 1800, (r - l) * 20);
            //printf("%d %d : %d\n", l + 1, r + 1, f[l][r]);
        }
    }
    vector<vi> dp(n, vi(n + 1, INF));
    vi mindp(n, INF);
    for (int i = 0; i < n; ++i)
    {
        dp[i][i + 1] = f[0][i];
        for (int j = 1; j <= i; ++j)
        {
            dp[i][j] = mindp[i - j] + f[i - j + 1][i];
        }
        for (int j = 0; j < (int)dp[i].size(); ++j)
            mindp[i] = min(mindp[i], dp[i][j]);
    }
    printf("%d\n", mindp[n - 1]);
    return 0;
}