>>295 Perl

use 5.18.2;
use bigint;
my $last = 481026574172857371038510295691740138639173281038463829385710488361648301846283405837618447580;
say (++$last) * $last / 2;

結果:481026574172857371038510295691740138639173281038463829385710488361648301846283405837618447581