#include <fstream>
using namespace std;
ifstream fin("nrlipsa2.in");
ofstream fout("nrlipsa2.out");
int i,n,x,j,y,v[201];
int main()
{
while (fin>>x)
{
if (x<=100 && x>=-100 )
v[x+100]=1;
}
for (i=0;i<=200;i++)
{
if (v[i]==0)
{
y=1;
fout<<(i-100);
i=201;
}
}
if (!y)
fout<<"nu exista";
}