#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <math.h>

const char * infile = "longnumber.inp";
const char *outfile = "longnumber.out";

int arr[2][201];
long long pos;
int ans;

int printll(long long c, int ss[])
{
	int i = 0;
	do {
		ss[i++] = c % 10LL;
		c /= 10LL;
	} while (c);
	return i;
/*	while (i>=0) {
		printf("%d", ss[i]);
		i--;
	}*/
}

void printqq(long long c)
{
	int ss[100];
	int i = 0;
	do {
		ss[i++] = c % 10LL;
		c /= 10LL;
	} while (c);
	i--;
	while (i>=0) {
		printf("%d", ss[i]);
		i--;
	}
//	printf("\n");
}


int mylog10(long long x)
{
	int c = 0;
	while (x>=10LL) {
		x/=10LL;
		c++;
	}
	return c;
}

int exp10(int x)
{
	int p = 1;
	for (int i = 0; i < x; i++)
	p*=10;
	return p;
}


long long countdigs(int x)
{
	if (x < 10) return (x-1);
	int p = 1;
	int c = 1;
	long long all = 0LL;
	while (p *10 <= x) {
		all += (long long) ((p*10)-(p)) * c;
		p *= 10;
		c++;
	}
	all += (x-p)*c;
	return all;
}
int step = 10000;
long long countdigs1(int x)
{
	long long all=0;
	for (int i = 1; i < x;) {
		step =  10000;
		int f1, f2, n;
		//do {
			step /= 2;
			step >?= 1;
			n = i + step;
			n <?= x-1;
			long long q = i;
			q = q*q;
			f1 = mylog10(q)+1;
			q = n;
			q = q*q;
			f2 = mylog10(q)+1;
		//}while (f1 != f2 || n > i + 100); 
		if (f1 != f2 || n >= x) {
			for (int j = i; j <= n; j++) {
				long long gog = j;
				gog *= gog;
				all += mylog10(gog) + 1;
			}
		} else {
			all += (n-i+1)*f1;
		}
		i = n + 1;
		//all += mylog10(q)+1;
	}
	return all;
}


void solve(void)
{
	int x[1000];
	long long gpos = 0;
	for (int n = 1; ; n++) {
		int r = printll(n, x);
		for (int i = r-1; i >= 0; i--) {
			if (gpos>= pos-100LL && gpos <= pos+100LL) {
				arr[0][gpos-pos+100LL] = x[i];
			}
			gpos++;
		}
		if (gpos > pos + 100LL) {
//			printf("cycle 1 broken at %d\n", n);
			break;
		}
		
	}
	gpos = 0;
	for (int n = 1; ; n ++) {
		long long xx = n;
		xx *= xx;
		int r = printll(xx, x);
		for (int i = r-1; i >= 0; i--) {
			if (gpos>= pos-100LL && gpos <= pos+100LL) {
				arr[1][gpos-pos+100LL] = x[i];
			}
			gpos++;
		}
		if (gpos > pos + 100LL) {
//			printf("cycle 1 broken at %d\n", n);
			break;
		}
	}
	int carry = 0;
	for (int i = 200; i >= 0; i--)
	{
		arr[1][i] += arr[0][i] + carry;
		carry = arr[1][i] / 10;
		arr[1][i] %= 10;
	}
	ans = arr[1][100];
}

int b1n(int l, int r, long long (*fun) (int), long long target)
{
	long long lt, rt;
	lt = fun(l);
	rt = fun(r);
	while (r-l>3) {
		int m = (int) (l + (r-l)*((double)(target-lt)/(rt-lt)));
		if (m==l) m++;
		if (m==r) m--;
		long long mt = fun(m);
		if (mt < target) {
			l = m;
			lt = mt;
		}
		else {
			r = m;
			rt = mt;
		}
		
	}
	return (l+r)/2;
}

void dowork(int *arr, long long (*fun) (int), int right, bool sqr = false) 
{
	int x[1000];
	int l = b1n(0, right, fun, pos-120);
 	int ro = b1n(0, right, fun, pos+120);
// 	printf("will scan from %d to %d;", l, ro);
 	long long gpos = fun(l);
 //	printf("gpos = "); printqq(gpos);printf("\n");
	for (int n = l; ; n++) {		
		long long pp = n;
		if (sqr) pp*=pp;
		int r = printll(pp, x);
		for (int i = r-1; i >= 0; i--) {
			if (gpos>= pos-100LL && gpos <= pos+100LL) {
				arr[gpos-pos+100LL] = x[i];
			}
			gpos++;
		}
		if (gpos > pos + 100LL) {
//			printf("cycle 1 broken at %d\n", n);
			break;
		}
		
	}
 	
}

void solve2(void)
{
	int x[1000];
	dowork(arr[0], countdigs, 300000000);
	dowork(arr[1], countdigs1, 150000000, true);
	int carry = 0;
	for (int i = 200; i >= 0; i--)
	{
		arr[1][i] += arr[0][i] + carry;
		carry = arr[1][i] / 10;
		arr[1][i] %= 10;
	}
	ans = arr[1][100];
}


int main(void)
{
	unsigned ppos;
	FILE *f = fopen(infile, "rt");
//	FILE *f = stdin;
	FILE *out = fopen(outfile, "wt");
//	FILE *out = stdout;
	while (1 == fscanf(f, "%ud", &ppos)) {
		long t = clock();
//		printf("pos = %u\n", ppos);
		pos = ppos;
		pos--;
		if (pos < 10000)
			solve();
		else
			solve2();
		fprintf(out, "%d\n", ans);		
//		printf(" (%d secs)\n", clock()-t);
	}
//	system("pause");
	fclose(f);
	fclose(out);
/*	int x;
	while (1) {
		scanf("%d", &x);
		printf("to num x there are ");
		printqq(countdigs(x));printf(" digits\n");
		printf("to num x there are ");
		printqq(countdigs1(x));printf(" digits1\n");
		
		
	}*/
}