#include<fstream.h>
#include<math.h>
int v[1000001];
int main()
{
ifstream f("fractii.in");
ofstream g("fractii.out");
long i,n,j;
f>>n;
for (i=2;i<=n;i+=2) v[i]=1;
for (i=3;i<=sqrt(n);i+=2)
   {
   v[i-1]=1;
   if (v[i]==0)
     {
     for (j=i*i;j<=n;j+=i)  v[j]=1;
     }
   }
if (n%2==0) v[n]=1;
v[2]=0;
g<<n;
f.close();
g.close();
return 0;
}