#include <stdio.h>

void print_res(FILE *out, int res) {
  if (res <= 0) {
    res = 1;
  }
  fprintf(out, "%d", res);
}

int num_fives(long i) {
  int res = 0;
  while (i % 5 == 0) {
    res++;
    i /= 5;
  }
  return res;
}

int main(void) {
  FILE *in = fopen("fact.in", "r");
  FILE *out = fopen("fact.out", "w");

  int n;
  int curr = 0;
  fscanf(in, "%d", &n);
  // fprintf(out, "%d\n", n);
  
  for (long i = 5; ; i += 5) {
    if (curr >= n) {
      print_res(out, i - 5);
      break;
    }

    curr += num_fives(i);
    // fprintf(out, "%ld----%d\n", i, curr);
  }

  fclose(in);
  fclose(out);
  return 0;
}