#include <bits/stdc++.h>

using namespace std;
ifstream fin("secv5.in");
ofstream fout("secv5.out");
int i,n,k,a,b,dif,v[500001],x,act,s,nr,l,u,f[100001];
int main()
{
    fin>>n>>l>>u;
    for(i=1;i<=n;i++)
        {fin>>v[i];f[v[i]]++;if(f[v[i]]==1)nr++;}
    for(i=l;i<=u;i++)
        s+=i;
    fout<<s+nr;
    return 0;
}