#include <stdio.h>

int main()
{
  int i,j,cksum=0,n=6;

  while (scanf("%1d%1d",&i,&j),n--) {
    cksum+= i+3*j;
  }

  cksum = 9-((cksum-1)%10);
  printf("%d\n", cksum);

  return 0;
}