v a r   i n p u t N u m   =   p r o m p t ( " H  y   n h  p   m t   s   t r o n g   k h o n g   t   5 0   n   1 0 0 : " ) ; 
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 i f   ( i s N a N ( i n p u t N u m ) )   { 
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                 a l e r t ( " D    n    l    m t   s ,   n    k h  n g   t h c   l    m t   s   v i   t  i . " ) ; 
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         }   e l s e   { 
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                 a l e r t ( i n p u t N u m   +   "   k h  n g   p h i   l    m t   s . " ) ; 
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 e l s e   i f   ( ( i n p u t N u m   >   9 9 )   | |   ( i n p u t N u m   <   5 1 ) )   { 
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         a l e r t ( " S   "   +   i n p u t N u m   +   "   k h  n g   n m   t r o n g   k h o n g   t   5 0   n   1 0 0 . " ) ; 
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