#include <fstream>
#include <iostream>
using namespace std;
int p, n;
int zerouri(int x){
    int c=0, i2;
    //cout<<"\n testing: "<<x<<"... ";
    for(int i=1;i<=x;i++)
    {
        i2=i;
        while(i2 && i2%5==0)
            c++, i2/=5;
    }
    //cout<<c;
    return c;
}
int main(){
    ifstream f("fact.in");
    ofstream g("fact.out");

    f>>p;
    if(p==0) g<<"1";
    else
    {
        int m=2;
        while(zerouri(m)<p)
            m++;
        if(zerouri(m)!=p)
            g<<"-1";
        else
            g<<m;
    }
    return 0;
}