$.$ Determine the Big$-\backslash$Theta complexity of func$2()$ as a function of n assuming the task$($a$,$b$)$ is

O$(1).$ Prove your answer. Use sigma notation $(\backslash$Sigma $).$

Algorithm $2$

def func$2($n$)$:

for i in range$(1,$ n $+1)$:

for j in range$($i$,1+($i $$ n$))$:

task$($i $+1,$ j$)$