#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

void ss(vector<int> &sums, vector<int> &y, vector<int> &yy){
  int n = y.size();
  rrep(i, n){
    int ad;
    if(y.at(i) < yy.at(i)) ad = 1;
    else if(y.at(i) == yy.at(i)) ad = 0;
    else ad = -1;
    sums.at(i) = sums.at(i+1) + ad;
  }
}

int main(){
  int n;
  cin >> n;
  vector<int> y(n);
  rep(snip_i, n) cin >> y.at(snip_i);
  vector<int> sums(n+1, 0);
  vector<int> yy(n, 1e4);
  vector<int> ans(n);
  rep(i, n){
    ans.at(i) = yy.at(i) - y.at(i);
  }
  int r = n;

  while(r > 0){
    ss(sums, y, yy);
    rep(i, r){
      int d = yy.at(i) - y.at(i);
      if(d > 0){
        yy.at(i)--;
        continue;
      }
      // int cost = -1;
      // rep2(j, i+1, r){
      //   if(yy.at(j) - y.at(j) > 0) cost++;
      //   else if(yy.at(j) - y.at(j) == 0){
      //   }else cost--;
      //   if(cost > 0) break;
      // }
      int cost = sums.at(i);
      if(cost > 0) yy.at(i)--;
      else{
        r = i;
        break;
      }
    }
  }
  int aa = 0;
  rep(i, n){
    // cerr << yy.at(i) << " ";
    aa += abs(yy.at(i) - y.at(i));
  }
  // cerr << endl;
  cout << aa << endl;
  return 0;
}