How to calculate the amount of 1! +2! +3!+...+N!

for this natural n calculate the amount of 1! +2! +2!+...+n!. In solving this problem, only one cycle can be used. It is forbidden to use the mathematical library in this task.

  n =  int  ( input  ()) n =  1    sum  =  0    for  a  in   range  ( 1 , n+ 1 ):   for  b  in   range  ( 1 , a + 1 ):  n = n * b  sum  += " N  print  ( sum )     
, however, my solution does not come out. Tell me how to solve correctly?