Daca 10^k<=x<10^(k+1), k apartine N, atunci [lg(x)]=k.
(mentionez ca [a] reprezinta partea intreaga a numarului real a).
In cazul nostru avem:
10^0<=1,2,...,9<10^1, deci [lg1]=[lg2]=...=[lg9]=0.
10^1<=10,11,...,99<10^2, deci [lg10]=[lg11]=...=[lg99]=1.
10^2<=100,101,...,999<10^3, deci [lg100]=[lg101]=...=[lg999]=2.
10^3<=1000,1001,...,2012<10^4, deci [lg1000]=[lg1001]=...=[lg2012]=3.
Obtinem astfel A=9*0+90*1+900*2+1013*3=0+90+1800+3039=4929.
