#include <bits/stdc++.h>
using namespace std;

int main(){
    string S;
    cin>>S;
    int a=7;if(S.size()<7)a=stoi(S);
    switch(a){
        case 5:cout<<3<<endl;break;
        case 6:cout<<5<<endl;break;
        default:cout<<7<<endl;break;
    }

    return 0;
}