#include <iostream>
#include <fstream>
using namespace std;

int a[126];

int main()
{
    int  n = 0, p, contor, j = 0;
    ifstream fin("fact.in");
    fin>>p;

    while(n/5 < p - 1)
        n++;
    for(int i=1; i<=n; i++)
        if(i%5 == 0)
            a[j++] = i;

    contor = j;
    for(int i=0; i<j; i++)
          if(a[i]%25 == 0)
            contor++;

    if(contor*p == n)
        n = -1;
    if(contor*p < n)
        n = n+5;
    ofstream fout("fact.out");
    fout<<n;
    fout.close();

    return 0;
}