#include <stdio.h>

using namespace std;

FILE*f=fopen("fact.in","r");
FILE*g=fopen("fact.out","w");

int main()
{
    long long p,n,nr=0,z,m;
    fscanf(f,"%d",&p);
    n=p*5;
    nr=0;
    z=5;
    while (z<=n)
    {
        nr=nr+n/z;
        z=z*5;
    }
    while (nr>p)
    {
        m=n;
        while (m%5==0) {m=m/5;nr--;}
        n=n-5;
    }
    fprintf(g,"%d",n);
    fclose(g);
    return 0;
}