#include <fstream>
#include<iostream>
using namespace std;
long factorial(long n, long r,long i)
{
    long j;j=r;
    if(r%5==0)
    do{ i+=1;j=j/5;}while(j%5==0);
    if(i==n)return r;
    if(i>n)return -1;
    factorial(n,r+1,i);
}
int main()
{
    ifstream in;in.open("fact.in");
    ofstream ou;ou.open("fact.out",ofstream::out);
    long n,i,r;
    r=1;
    in>>n;i=0;
    if(n==0)ou<<1;
    else
    ou<<factorial(n,r,i);
    in.close();ou.close();
    return 0;
}