#include<stdio.h>

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

int p;

int nr2(int x)
{
 int nr=0;
 while(x%2==0)
  {
   nr++;
   x/=2;
  }
 return nr;
}

int nr5(int x)
{
 int nr=0;
 while(x%5==0)
  {
   nr++;
   x/=5;
  }
 return  nr;
}

void fact()
{
 int x=1,i=1,ok=0,a,b;
 while(ok==0)
  {
   int s1=0,s2=0;
   for(i=1;i<=x;i++)
    {
     a=nr2(i);
     b=nr5(i);
     s1=s1+a;
     s2=s2+b;
    }
   if((s1<s2 && s1==p) || (s2<s1 && s2==p))
    ok=1;
   else
    x++;
  }
 fprintf(out,"%d",x);
}

int main()
{
 fscanf(in,"%d",&p);
 fact();
 return 0;
}