#include<fstream>
#include<iostream>
using namespace std;
int main()
{int i,a,n,s,t,j,v[200];
ifstream f("nrtri.in");
ofstream g("nrtri.out");
f>>n; cout<<n;
for(i=1;i<=n;i++)
	{f>>a;
	v[a]=1;}
	i=1;
	cout<<v[2];
do	
{if (v[i]==1)
    j=i+1;
while((v[j]!=1)&&(j<=800))
	{j++;}
if (j<=800)
{for (t=j+1;t<=i+j;t++)
	s+=v[t];
}
i++;}
while(i<=800);
g<<s<<endl;
return 0;
f.close();
g.close();}