#include <stdio.h>

#define IN "fact.in"
#define OUT "fact.out"

FILE *fin=fopen(IN,"r");
FILE *fout=fopen(OUT,"w");

using namespace std;

long long int n;
long long int sol;

int desc(long long int);

int main()
{
 fscanf(fin,"%lld",&n);
 fclose(fin);

 while(n>0)
 {
  sol+=5;
  n-=desc(sol);
 }

 fprintf(fout,"%lld",sol);
 fclose(fout);

 return 0;
}

int desc(long long int val)
{
 int c=0;

 while(val%5==0 && val)
 {
  c++;
  val/=5;
 }
 return c;
}