if: Bad syntax error (Scheme programming)

if: Bad syntax error (Scheme programming)

(define generalized-triangular
(lambda(input n)
(if(= n 1)
1
(+ (input n) (generalized-triangular(- n 1))))))
This program is designed to take a number and a function as inputs and do
the following..
f(1) + f(2) + f(3)+ ... + f(N).
An example input would be ...
(generalized-triangular square 3)
The Error message:
if: bad syntax;
has 4 parts after keyword in: (if (= n 1) 1 (+ (input n)
(generalized-triangular (- n 1))) input)
Thanks very much in advance!