#include<stdio.h>
int main ()
{
freopen("fact.in","r",stdin);
freopen("fact.out","w",stdout);
int l1=1,l2=1000000000,p,pp=0,n,i,s;
scanf("%d",&p);
while(l1<l2&&pp==0)
    {n=(l2+l1)/2;
    s=0;
    for(i=5;i<=n;i*=5)
        s+=n/i;
    if(s==p)
            pp=1;
    else
        if(s>p)
            l2=n-1;
        else
            l1=n+1;
    }
    if(n<5)
    printf("1");
else{
if(n%5==0)
    printf("%d",n);
if(n%5==1)
    printf("%d",n-1);
if(n%5==2)
    printf("%d",n-2);
if(n%5==3)
    printf("%d",n-3);
if(n%5==4)
    printf("%d",n-4);
return 0;}
}