Convolution of Fejer kernel

I have a question about how to prove $$|p(y)|leq 3int_{T^2}|p(y-z)|K_N(z)dz$$ where $p(y)=sum_{|n|<N}a_n e^{iny}$ and $K_N(y)=sum_{|n|<N}frac{N-|n|}{N}e^{iny}$?