#include <stdio.h>
#include <stdlib.h>

int main(){
  unsigned long long n,i,pas,s,si;
  FILE *fin,*fout;
  fin=fopen("fact.in","r");
  fout=fopen("fact.out","w");
  fscanf(fin,"%lld",&n);

  pas=1<<30;
  i=0;
  while(pas>0){
    s=0;
    si=i+pas;
    while(si>0){
      s+=si/5;
      si/=5;
    }
    if(s<n){
      i+=pas;
    }
    pas/=2;
  }

  fprintf(fout,"%lld",i+1);


  fclose(fin);
  fclose(fout);
  return 0;
}