#include <fstream>
#include <iostream>
#include <math.h>

using namespace std;

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

int F(long long n)
{
    int result=0;
    long long exp=5;
    while(n>=exp)
    {
        result+=n/exp;
        exp*=5;
    }
    return result;
}

int main()
{
    int N;
    f>>N;

    if(N==0) g<<1;
    else
    {
        long long m,a=0,b=9223372036854775807;
        while(a<b)
        {
            m=((a-b)>>1)+b;
            if(F(m)<N) a=m+1;
                else b=m-1;
        }
        g<<a;
    }

    return 0;
}