#include <stdio.h>

char num[81];
int len, halflen;

void process(void);

int myinc(int pos) {
  int i;
  if(pos>=0) {
    if(num[pos]!='9')
      num[pos]++;
    else {
      num[pos] = '0';
      myinc(pos-1);
    }
	return 0;
  } else {
    for(i=len; i>0;i--) num[i] = num[i-1];
    num[0] = '1';
    len++;
    num[len] = 0;
    halflen = len >> 1;
	return 1;
  }
}

void decrease(int a) {
  int can = 0, i, p;
  for(p=halflen; p<len; p++) if(num[p] != '9') break;
  for(i=p+1; i<len; i++) can += num[i] - '0';
  if(can) can--;
  if(can>=a) {
    for(i=len-1; i>=halflen; i--) {
      if(num[i]-'0' > a) {
        num[len-1] = num[i]-a-1;
        if(i != len-1) num[i] = '0';
        myinc(i-1);
        return;
      } else {
        a -= num[i]-'0';
        num[i] = '0';
      }
    }
  } else {
    if(myinc(p-1)) p++;
    for(i=p; i<len; i++) num[i] = '0';
    process();
  }
}

void increase(int a) {
  int can = 0, i;
  for(i=halflen; i<len; i++) can += '9' - num[i];
  if(can>=a) {
    for(i=len-1; i>=halflen; i--)
      if('9'-num[i] > a) {
        num[i] += a;
        break;
      } else {
        a -= '9'-num[i];
        num[i] = '9';
      }
  } else {
    myinc(halflen-1);
    for(i=halflen; i<len; i++) num[i] = '0';
    process();
  }
}

void process(void) {
  int left = 0, right = 0, i;
  for(i=0; i<halflen; i++) left += num[i]-'0';
  for(i=halflen; i<len; i++) right += num[i]-'0';
  if(left==right) return;
  if(left>right)
    increase(left-right);
  else
    decrease(right-left);
}

int main(void) {
  int i;
  char c = '0';
  while(c=='0') scanf("%c", &c);
  for(i=0; c!='\n'; i++) {
    num[i] = c;
    scanf("%c", &c);
  }
  if(i) {
    num[i] = 0;
    len = i;
    halflen = len>>1;
    process();

    printf("%s\n", num);
  } else
    printf("0\n");
  return 0;
}