/*

     题意：问最少增加多少值使变成递增序列

     贪心：排序后，每一个值改为前一个值+1，有可能a[i-1] = a[i] + 1，所以要 >=

 */

 #include <cstdio>

 #include <cstring>

 #include <algorithm>

 using namespace std;

 typedef long long ll;

 const int MAXN = 3e3 + ;

 const int INF = 0x3f3f3f3f;

 int a[MAXN];

 int main(void)        //Codeforces Round #304 (Div. 2) B. Soldier and Badges

 {

     int n;

     while (scanf ("%d", &n) == )

     {

         for (int i=; i<=n; ++i)    scanf ("%d", &a[i]);

         sort (a+, a++n);

         int tot = ;    a[] = ;

         for (int i=; i<=n; ++i)

         {

             if (a[i-] >= a[i])    {tot += (a[i-] - a[i] + ); a[i] = a[i-] + ;}

         }

         printf ("%d\n", tot);

     }

     return ;

 }

 /*

 4

 1 3 1 4

 5

 1 2 3 2 5

 4

 4 3 2 2

 */