#include <stdio.h>

int main()
{
  unsigned long long ean;
  int digit, cksum=0;

  scanf("%Ld",&ean);
  while (ean) {
    digit=ean%10; ean/=10;
    cksum+=3*digit;
    digit=ean%10; ean/=10;
    cksum+=digit;
  }
  cksum=9-((cksum-1)%10);
  printf("%d\n", cksum);

  return 0;
}