#include <fstream>

using namespace std;

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");

    int p;
    f >> p;

    int div2=0, div5=0, n=1;
    while(div2<p || div5<p)
    {
        int x=n;
        while(x%2==0)
        {
            x=x/2;
            div2++;
        }
        int y=n;
        while(y%5==0)
        {
            y=y/5;
            div5++;
        }
        bool ok=0;
        if(div2<div5) if(div2==p){break; ok=1;}
        if(div5<div2) if(div5==p){break; ok=1;}
        if(ok==0) n++;
    }
    bool ok=0;
    if(div2<div5) if(p!=div2){g << -1; ok=1;}
    if(div5<div2) if(p!=div5){g << -1; ok=1;}
    if(ok==0) g << n;
}