how many different positive integers exist between 10 ^ 5 and 10 ^ 6 , the sum of whose digits is equal to 2 ?
"so , the numbers should be from 100,000 to 1 , 000,000 the following two cases are possible for the sum of the digits to be 2 : 1 . two 1 ' s and the rest are 0 ' s : 100,001 100,010 100,100 101,000 110,000 5 numbers . 2 . one 2 and the rest are 0 ' s : 200,000 1 number . total = 6 numbers . answer : a"
add(add(const_4, const_3), const_1)