#include<iostream>
#include<cstdio>
using namespace std;
int n,ok;
int main()
{
    int i,d;
    cin>>n;
    if (n<=4)
    {
        if (n==1) cout<<"0\n";
        if (n==2) cout<<"1\n";
        if (n==3) cout<<"2\n";
        if (n==4) cout<<"2\n";
        return 0;
    }
    for (d=2;d*d<=n && !ok;++d)
        if (n%d==0)
            ok=1;
    if (!ok)
        cout<<n-1<<"\n";
    else
    {
        cout<<"0\n";
    }
    return 0;
}