S= 2^1 +2^2 + ... + 2^2012
2S= 2^2 + 2^3 + ... + 2^2013
2S - S= (2^2 + 2^3 + ... + 2^2013) - (2^1 + 2^2 +... + 2^2012)
S= 2^2013 - 2^1 (asta ramane dupa scadere)
S= 2^2013 - 1
U(ultima cifra) 2^x = 2, 4, 8, 6 (se repeta din 4 in 4)
2013:4=503 rest 1 => U (x^2013 =1) => U (2^2013 -1) =1-1 =0
Raspuns: 0.