//
// main.c
// fact2
//
// Created by Alexandru Bâgu on 1/12/14.
// Copyright (c) 2014 Alexandru Bâgu. All rights reserved.
//
#include <stdio.h>
typedef long long int __long;
int powOf5(__long n)
{
int p = 0;
if(n % 5 == 0 && n > 0 )
return p = 1 + powOf5(n / 5);
return p;
}
int fives(__long n)
{
int k = 0;
while(n > 4) k += powOf5(n--);
return k;
}
int isValid(__long n, int p)
{
int k = fives(n);
if(p >= k) return 1;
return -1;
}
int main(int argc, const char * argv[])
{
freopen("fact.in", "r", stdin);
freopen("fact.out", "w", stdout);
int p;
scanf("%d", &p);
if(p == 0)
{
printf("1");
return 0;
}
p--;
__long max = 5 * p;
__long k = 1 << 30, i = 0;
while(k > 0)
{
if(k + i <= max)
if(isValid(k + i, p))
i += k;
k >>= 1;
}
p++;
while(fives(i) < p)
i++;
printf("%lld", i);
return 0;
}