include[HTML_REMOVED]

using namespace std;
int main() {
int a;
cin>>a;
int f[a];
for(int i=0;i[HTML_REMOVED]>f[i];
}
sort(f,f+a);
int e=f[0]-1;
int u=0;
int r=0;
for(int i=0;i<a;i){
if(e+1==f[i]){
u;
e++;

   }else{
    if(e!=f[i]){
            r=1;
        cout<<u;
        break;
       }
   }

}
if(r==0){
cout<<u;
}
return 0;
}