#include<stdio.h>
FILE *f=fopen("fact.in","r"),
     *g=fopen("fact.out","w");
long long p,n,i,v,m,ok;
long long zero(long long n)
{ long long q=5,k=0;
  while(q<n) { k+=n/q;
	       q*=5;
	     }
  return k;
}
int caut(long long k)
{ while(k%5) --k;
  return k;
}

int main()
{ fscanf(f,"%lld",&p);
  n=20000000;
  long long left=1,right=n;
  ok=1;
  while(left<right&&ok){ m=(left+right)>>1;v=zero(m);
			  if(v==p) n=caut(m),ok=0;
			  else if(v>p) right=m;
			       else left=m;
			}
  if(!ok)fprintf(g,"%lld\n",n);
  else fprintf(g,"0\n");
  fclose(f);
  fclose(g);
  return 0;
}