#include <bits/stdc++.h>

using namespace std;

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

long long cer,n,x,cinci;

void fcinci()
{
    while(x % 5 == 0)
    {
        ++ cinci;
        x /= 5;
    }
}
int main()
{
    f >> cer;
    if(!cer)
    {
        g << 1;
        return 0;
    }
    n = 1;
    while(1)
    {
        x = n;
        fcinci();
        if(cinci == cer)
        {
            g << n;
            return 0;
        }
        if(cinci > cer)
        {
            g << -1;
            return 0;
        }
        ++ n;
    }
}