include <iostream>

include <vector>

using namespace std;

int main() {
int n;
cin >> n;

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

vector<vector\<int>> f(n + 1, vector<int>(max(a) + 1));

for (int i = 0; i <= n; i++) {
for (int j = 0; j <= max(a); j++) {
if (i == 0) {
f[i][j] = 0;
} else {
f[i][j] = min(
f[i - 1][j],
f[i - 1][j - 1] + (j - a[i - 1]),
f[i - 1][j + 1] + (a[i - 1] - j)
);
}
}
}

cout << f[n][a[n - 1]] << endl;

return 0;
}