program main
implicit None
	integer(8)::n,p=0,i
	character(len =100)::a,b,c
	
	read*,n
	read*,a,b,c
	
	do i = 1,n
		if(a(i:i) == b(i:i))then
			if(a(i:i) /= c(i:i)) p = p+1
			else
				if(a(i:i) == c(i:i))then
					p = p+1
					else if(b(i:i) == c(i:i))then
					p = p+1
					else
					p = p+2
				endif
		endif
	enddo
	
	print "(i0)",p
end program main