#include <cstdio>

using namespace std;

int p;

int zero(int x)
{
    int s=0;

    while(x/5!=0)
    {
        s+=x/5;
        x/=5;
    }
    return s;
}

int cautbin(int lg,int p)
{
    int i;
    for(i=0;lg!=0;lg>>=1)
    {
        if(i+lg<=100000000 && zero(i+lg)>=p)
            i+=lg;
    }
    return i;
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);

    scanf("%d",&p);
    printf("%d",cautbin(134217728,p));
    return 0;
}