## Javascript (<s>94</s> <s>92</s> <s>87</s> 86) ##

 do{n=0;for(i in a){n+=a[i]*a[i]|0}a=n+''}while(n>4);alert(['H','Unh'][n>1?1:0]+'appy')


Input is provided by setting a to the number desired.

Credits to mellamokb.