#include <iostream>
#include <fstream>
 
using namespace std;
 
ifstream f("fact.in");
ofstream g("fact.out");
 
int main()
{
    long long p,x,a;
    f>>p;
    if(p==0){
        g<<0;
        return 0;
    }
    x=1;
    a=2;
    while(x<p){
        if(a%1953125==0) x+=10;
        else if(a%390625==0) x+=9;
        else if(a%78125==0) x+=8;
        else if(a%15625==0) x+=7;
        else if(a%3125==0) x+=6;
        else if(a%625==0) x+=5;
        else if(a%125==0) x+=4;
        else if(a%25==0) x+=3;
        else if(a%5==0) x+=2;
        else x++;
        a++;
    }
    a--;
    if(x==p) g<<a*5;
    else g<<-1;

    return 0;
}