#include <stdio.h>
int main()
{ long long st=10000000,p,mid,dr=1,e=0;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
  scanf("%lld",&p);
  while(st<=dr)
  { mid=st+(dr-st)/2;
    int a=mid;
    while(a!=0||a%5!=0){ a/=5;e++;}
    if(p<e) dr=mid-1;
    else if(p>e) st=mid+1;
     if(p==e) return mid;
     }
   return -1;
}