//#define _GLIBCXX_DEBUG
#include "bits/stdc++.h"

using namespace std;

//------------------------------- Libraries --------------------------------//

//------------------------------- Type Names -------------------------------//

using i64 = int_fast64_t;

using seika = string;
//{akari : 1D, yukari : 2D, maki : 3D} vector
template <class kizuna>
using akari = vector<kizuna>;
template <class yuzuki>
using yukari = akari<akari<yuzuki>>;
template <class tsurumaki>
using maki = akari<yukari<tsurumaki>>;
//{akane : ascending order, aoi : decending order} priority queue
template <class kotonoha>
using akane = priority_queue<kotonoha, akari<kotonoha>, greater<kotonoha>>;
template <class kotonoha>
using aoi = priority_queue<kotonoha>;

//------------------------------- Dubug Functions ---------------------------//
inline void print()
{
    cout << endl;
}
template <typename First, typename... Rest>
void print(const First &first, const Rest &... rest)
{
    cout << first << ' ';
    print(rest...);
}
//------------------------------- Solver ------------------------------------//

void solve()
{
    int n;
    cin >> n;
    akari<int> bs(n);
    for (int i = 0; i < n; i++)
    {
        cin >> bs[i];
    }
    i64 ans = 0, r = 0;
    for (int l = 0; l < n; l++)
    {
        while (r < n && bs[r] == 0)
        {
            r++;
        }
        bs[r]--;
        ans += abs(r - l);
    }
    cout << ans << endl;
}

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