#include <cstdio>

using namespace std;

FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");

int n;

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

int rez1()
{
    int pas=1<<30,r=0;
    while(pas!=0)
    {
        if(cifre(r+pas)<n)
            r+=pas;
         pas/=2;
    }
    return r;
}

int main()
{
    int x;
    fscanf(f,"%d",&n);
    x=rez1()+1;
    fprintf(g,"%d",x);
    return 0;
}