#include <iostream>
#include <cstdio>
using namespace std;
const int NC=1000;
int zero(int n){
    int nr=0;
    while(n>=5)
        nr+=(n/=5);
    return nr;
}
int main()
{
    int p;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    cin>>p;
    int nr=0,i;
    for(i=(1<<30);i>0;i/=2)
        if(zero(i+nr)<p)
            nr+=i;
    if(i<=0)
        cout<<-1;
    else
        cout<<nr+1;

    return 0;
}