Let $f(x) = x^7 + ax^3 + cx$  If $f(5) = 3,$ then find $f(-5).$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Let $f(x) = x^7 + ax^3 + cx$  If $f(5) = 3,$ then find $f(-5).$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
-3
Let $f(x) = x^7 + ax^3 + cx$  If $f(5) = 3,$ then find $f(-5).$
train