#include <iostream>
#include <fstream>
#define maxval 100000000
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int NmbOfZero(int i)
{
    int exp=5, zero=0;
    while(exp<i)
    {
        zero+=i/exp;
        exp*=5;
    }
    return zero;
}
int main()
{
    int p, l=1, r=maxval,ans=0;
    in>>p;
    bool f=false;
    if(p==0)
    {
        out<<1<<"\n";
        return 0;
    }
    while(!f&&l<r)
    {
        int m=(l+r)/2,tmp=NmbOfZero(m);
        if(tmp==p)
        {
            ans=m;
        }
        if(tmp>=p)
            r=m-1;
        else
            l=m;
    }
    out<<ans<<"\n";
    return 0;
}