using namespace std;
#include<cstdio>
unsigned long p,nr,x;



int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%li",&p);

    while(p)
            {
            nr++;
            p--;
            x=nr;
            while(x%5==0 && p) {p--;x=x/5;}
            }
    if(nr)
    printf("%li\n",nr*5);
    else printf("1\n");
}