#include"bits/stdc++.h"
using namespace std;
#define REP(k,m,n) for(int (k)=(m);(k)<(n);(k)++)
#define rep(i,n) REP((i),0,(n))
using ll = long long;

int main()
{
	ll N;
	cin>>N;
	vector<ll> v(N);
	rep(i,N)cin>>v[i];

	ll res=0;
	priority_queue<ll,vector<ll>,greater<ll>> over,less;
	rep(i,N){
		switch(v[i]){
		case 0:
			less.push(i);
			break;
		case 1:
			break;
		default:
			rep(j,v[i]-1)over.push(i);
		}
		while(!over.empty()&&!less.empty()){
			res+=abs(over.top()-less.top());
			over.pop();
			less.pop();
		}
	}
	cout<<res<<endl;
	
	return 0;
}