#include<cstdio>
#include<cmath>
using namespace std;
int check(long long int n)
{
    int ok=0,p=1;
    for(int i=1;p!=0;i++)
    {
        p=(int)pow(5.0,i);
        p=n/p;
        ok+=p;
        //printf("%d %d\n",n,i);
    }
    return ok;
}
int main()
{
    long long int n;
    int p;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    for(n=1;n<=1<<31-1;n++)
    {
        if(p==check(n)) {printf("%lld",n); break;}
    }
    return 0;
}