//header{{{
#include<bits/stdc++.h>
  
using namespace std;
 
#define rep(i,n) for(int i=0;i<(n);++i)
#define reps(i,n) for(int i=1;i<=(n);++i)
#define all(x) (x).begin(),(x).end()
#define setout(n,x) setw(n) << setfill(x)
#define Fixed fixed << setprecision(10)
#define int long long
using pii = pair<int,int>;
constexpr int INF  = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr int mod = 1e9+7; 

template <class A, class B> inline bool chmax(A &a, const B &b) { return b > a && (a = b, true); }
template <class A, class B> inline bool chmin(A &a, const B &b) { return b < a && (a = b, true); }

template <class T> using min_heap = priority_queue<T,vector<T>,greater<T> >;
template <class T> using max_heap = priority_queue<T>;
 
int gcd(int a,int b){ return b ? gcd(b,a % b) : a;}
int lcm(int a,int b){ return a / gcd(a,b) * b;}
//}}}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin >> n;
	vector<int> b(n);
	min_heap<pii> que;
	rep(i,n){
		cin >> b[i];
		if(b[i] > 1) que.emplace(i,b[i]);
	}
	int cnt = 0;
	rep(i,n){
		if(b[i] == 0){
			pii x = que.top();
			que.pop();
			cnt += abs(i - x.first);
			x.second--;
			if(x.second > 1) que.emplace(x);
		}
	}
	cout << cnt << '\n';
	return 0;
}