#include<bits/stdc++.h>
using namespace std;

int main(){
	cin.tie(0),ios::sync_with_stdio(false);
	int n; cin>>n;
	vector<int>b(n); for(auto&&i:b)cin>>i;
	queue<int>zero; queue<pair<int,int>>rem;
	int64_t ans=0;
	for(int i=0;i<n;++i){
		if(b.at(i)==0)zero.push(i);
		else if(b.at(i)>1)rem.push({i,b.at(i)-1});
		while(rem.size()&&zero.size()){
			ans+=abs(rem.front().first-zero.front());
			--rem.front().second;
			if(rem.front().second==0)rem.pop();
			zero.pop();
		}
	}
	cout<<ans<<"\n"s;
}