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

int zero(long long n){
  long long nr=0;
  while(n>=5){
    nr+=n/5;
    n/=5;
  }
  return nr;
}


int main()
{
  long long i, pas, p;
  FILE *fi=fopen("fact.in", "r"), *fo=fopen("fact.out", "w");
  fscanf(fi, "%lld", &p);
  pas=1<<30;
  i=0;
  while(pas!=0){
    if(zero(i+pas)<=p-1)
      i+=pas;
    pas/=2;
  }
  fprintf(fo, "%lld", i+1);
  return 0;
}