import sys
native_input = input
input = lambda: sys.stdin.readline().strip()
import string
def solve():
n, = map(int, input().split())
a = list(map(int, input().split()))
a.sort()
l = []
ans = 0
for i in range(1, n):
if a[i - 1] == a[i]:
l.append(a[i])
elif a[i - 1] + 1 < a[i]:
for j in range(a[i - 1] + 1, a[i]):
if not len(l):
break
k = l.pop()
ans += j - k
if len(l):
for i in range(len(l)):
k = l.pop()
ans += a[-1] + 1 + i - k
print(ans)
solve()#include<bits/stdc++.h>
using namespace std;
#define endl "\n" ;
#define sort(v) sort(v.begin() , v.end());
#define reverse(v) reverse(v.begin() , v.end());
typedef pair<long long, long long > ii;
typedef vector<long long > vl;
typedef vector<int>vi ;
typedef vector<ii> vii;
typedef long long ll;
const int N = 1e6 + 5;
int oo = 100000;
ll const MOD = 1e9 + 7;
int dx[] = { 0, 1, -1,0 };
int dy[] = { 1,0 , 0,-1 };
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n ; cin >> n ;
vi v(n);
for (int i = 0 ; i < n ; i ++ )cin>>v[i];
sort(v);
int sol = 0 ;
for (int i = 1 ; i < n ; i ++ ){
for(int j = 0 ; j < i ; j ++ ){
if(v[i]==v[j]){
sol++;
v[i]++;
}
}
}
cout <<sol;
return 0;
}
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