// TEMPLATE
#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_set_char tree<char, null_type, less<char>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_set_string tree<string, null_type, less<string>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_multiset tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_multiset_char tree<char, null_type, less_equal<char>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_multiset_string tree<string, null_type, less_equal<string>, rb_tree_tag, tree_order_statistics_node_update>
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define int long long
#define ldouble long double
#define ll unsigned long long
// #define int int_fast32_t
#define endl '\n'
#define pii pair<int, int>
#define F first
#define S second
void solve()
{
int n;
cin >> n;
vector<int> vt(n + 1);
for(int i = 1; i <= n; i++){
cin >> vt[i];
}
deque<int> vt1, vt2;
for(int i = 1; i < n; i++){
if(vt[i] >= vt[i + 1]) vt1.push_back(i);
}
for(int i = 1; i < n; i++){
if(vt[i] <= vt[i + 1]) vt2.push_back(i);
}
int x = vt2.size() - 1;
int ans = INT_MAX;
for(int k = 1; k <= n; k++){
int cnt = 0;
for(int i = 0; i < vt1.size(); i++){
if(vt1[i] < k){
cnt += vt[vt1[i]] - vt[vt1[i] + 1] + 1;
}
}
for(int i = 0; i < vt2.size(); i++){
if(vt2[i] >= k){
cnt += vt[vt2[i] + 1] - vt[vt2[i]] + 1;
}
}
ans = min(ans, cnt);
}
cout << ans << endl;
}
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int T = 1;
// cin >> T;
while (T--)
solve();
}
