#include<cstdlib>
#include<cassert>
#include<cstdio>
#include<vector>
#include<queue>
#include<map>
#include<cctype>
#include<string>
#include<cstring>
#include<algorithm>
#include<unordered_set>
#include<unordered_map>
using namespace std;

#define fisier 0
#define consola 0

#if fisier
 #include<fstream>
 ifstream cin("fisier.in");
 ofstream cout("fisier.out");
#else
 #include<iostream> 
#endif


long long n,i;
bool t;

int main(){
    cin>>n; 
    
    if(n==4) cout<<"2";
    else{
    t=1;
    for(i=2;i*i<=n;i++)
      if(n%i==0) t=0;
      
    if(!t) cout<<"0";
    else cout<<n-1;
    }
    
    #if fisier
     cin.close();
     cout.close();
    #endif
    
    #if consola
     system("pause");
    #endif
    return 0;
}