#include <fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int main(){
    int p;
    fin>>p;
     if(p==0){
        fout<<1;
        return 0;
    }
    for(int i=0;i<=5*p;i+=5){
        int a=0;
        for(int j=5;j<=5*p;j*=5){
            a+=i/j;
        }
        if(a==p){
            fout<<i<<"\n";
            return 0;
        }
    }
    fout<<-1;
    return 0;
}