THIS IS ABSTRACT SYNTAX TREE FOR SIMPLE EXPRESSIONS.
 SAMPLE INPUT AND OUTPUT IS GIVEN BELOW

divay@divay-Vostro-3546:~/Abstract_Syntax_tree$ ./a.out

a=a+b;
( =  a ( +  a  b ))
a=1;
( =  a  1 )
a=b+c-s+1;
( =  a ( + ( - ( +  b  c ) s ) 1 ))
d=m+n-f*s+1*2;
( =  d ( + ( - ( +  m  n )( *  f  s ))( *  1  2 )))