+4/2 is not a valid number, removed it

Following are the stacktrace:

``` clojure
xumingmingv:blind(git:master)$ lein test
Exception in thread "main" java.lang.NumberFormatException: For input string: "+4", compiling:(blind/core.clj:45)
	at clojure.lang.Compiler.load(Compiler.java:6958)
	at clojure.lang.RT.loadResourceScript(RT.java:359)
	at clojure.lang.RT.loadResourceScript(RT.java:350)
	at clojure.lang.RT.load(RT.java:429)
	at clojure.lang.RT.load(RT.java:400)
	at clojure.core$load$fn__4890.invoke(core.clj:5415)
	at clojure.core$load.doInvoke(core.clj:5414)
	at clojure.lang.RestFn.invoke(RestFn.java:408)
	at clojure.core$load_one.invoke(core.clj:5227)
	at clojure.core$load_lib.doInvoke(core.clj:5264)
	at clojure.lang.RestFn.applyTo(RestFn.java:142)
	at clojure.core$apply.invoke(core.clj:603)
	at clojure.core$load_libs.doInvoke(core.clj:5298)
	at clojure.lang.RestFn.applyTo(RestFn.java:137)
	at clojure.core$apply.invoke(core.clj:603)
	at clojure.core$require.doInvoke(core.clj:5381)
	at clojure.lang.RestFn.applyTo(RestFn.java:137)
	at clojure.core$apply.invoke(core.clj:603)
	at user$eval75.invoke(NO_SOURCE_FILE:1)
	at clojure.lang.Compiler.eval(Compiler.java:6511)
	at clojure.lang.Compiler.eval(Compiler.java:6501)
	at clojure.lang.Compiler.eval(Compiler.java:6477)
	at clojure.core$eval.invoke(core.clj:2797)
	at clojure.main$eval_opt.invoke(main.clj:297)
	at clojure.main$initialize.invoke(main.clj:316)
	at clojure.main$null_opt.invoke(main.clj:349)
	at clojure.main$main.doInvoke(main.clj:427)
	at clojure.lang.RestFn.invoke(RestFn.java:421)
	at clojure.lang.Var.invoke(Var.java:419)
	at clojure.lang.AFn.applyToHelper(AFn.java:163)
	at clojure.lang.Var.applyTo(Var.java:532)
	at clojure.main.main(main.java:37)
Caused by: java.lang.NumberFormatException: For input string: "+4"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
	at java.lang.Integer.parseInt(Integer.java:449)
	at java.math.BigInteger.<init>(BigInteger.java:316)
	at java.math.BigInteger.<init>(BigInteger.java:451)
	at clojure.lang.LispReader.matchNumber(LispReader.java:402)
	at clojure.lang.LispReader.readNumber(LispReader.java:251)
	at clojure.lang.LispReader.read(LispReader.java:195)
	at clojure.lang.LispReader.readDelimitedList(LispReader.java:1135)
	at clojure.lang.LispReader$ListReader.invoke(LispReader.java:962)
	at clojure.lang.LispReader.readDelimitedList(LispReader.java:1126)
	at clojure.lang.LispReader$ListReader.invoke(LispReader.java:962)
	at clojure.lang.LispReader.readDelimitedList(LispReader.java:1126)
	at clojure.lang.LispReader$ListReader.invoke(LispReader.java:962)
	at clojure.lang.LispReader.read(LispReader.java:180)
	at clojure.lang.Compiler.load(Compiler.java:6949)
	... 31 more
Tests failed.
````