#include <stdio.h>

int main()
{
  int i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12;

  scanf("%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d",
	&i1, &i2, &i3, &i4, &i5, &i6, &i7, &i8, &i9, &i10, &i11, &i12);

  printf("%d\n", 9-(i1+i3+i5+i7+i9+i11+3*(i2+i4+i6+i8+i10+i12)-1)%10);

  return 0;
}