// yukicoder: No.491 10^9+1と回文
// 2019.5.11 bal4u

#include <stdio.h>

#define M 1000000000
int a[9] = { 0,9,18,117,216,1215,2214,12213,22212 };
int d[10];

#define MIN(a,b) ((a)<=(b)?(a):(b))
int main()
{
	int n, i, j, k, s, len, le, ans;
	long long N;

	scanf("%lld", &N);
	if (N <= M) { puts("0"); return 0; }
	n = (int)(N/(M+1)*(M+1)/M);
	len = 0, i = n; while (i) d[len] = i % 10, i /= 10, len++;
	ans = a[len-1], le = (len+1)>>1;
	for (i = 1; i < d[len-1]; i++) {
		s = 1; for (j = 1; j < le; j++) s *= 9;
		ans += s;
	}
	s = 1; for (j = 1; j < le; j++) s *= MIN(d[j], d[len-j-1]);
	ans += s;
	printf("%d\n", ans);
	return 0;
}