{ N=0; # use -vW=4 or 14
	for (i=1; ; i++) {
		window = substr($0,i,W)
		# compare each char of the window to rest of the window
		S = 0  # to count match
		for (j=1; j<W; j++) {
			for (k=j+1; k<=W; k++) {
				N++
				S+= (substr(window,j,1) == substr(window,k,1)) ? 1 : 0
			}
		}
		if (S == 0) {
			print i + W - 1, "(" N " loops)"
			next
		}
	}
} # O(N*W^2)