#include <fstream>

using namespace std;
ifstream f ("fact.in");
ofstream g ("fact.out");
long long nr=1,ok=1,n,nr2=0,nr5=0;
void apel1 (long long k)
{nr5++;k=k/5;
if (k%5==0)
return apel1(k);}
void apel2 (long long k)
{nr2++;k=k/2;
if (k%2==0)
return apel2(k);}
int main()
{   f>>n;
    while (ok)
    {if (nr%2==0)
    apel2(nr);
    if (nr%5==0)apel1(nr);
    if (nr2>=n&&nr5>=n)
    break;
    else
    nr++;
    }
    g<<nr<<'\n';
    return 0;
}