n = 1000000000
summe = 0 ;
for i = 1: n
    summe = summe + i ;
end % for i

summe

probe = 1/2 * n * (n+1)

summe_abwaerts = 0 ;
for i = n: -1 : 1
    summe_abwaerts = summe_abwaerts + i ;
end % for i
summe_abwaerts
