Well, you don't seem to understand the importance of telling us the details. Because of that, I gave you pseudo-code.
While we may some day all become high level telepaths, our mind reading skills are not yet fully developed.
You don't need to declare it. Use the code you already had! (I assume that code was working?)
int pressed = GPIOA->IDR & 0x000000001;
Note that this isn't using CMSIS but is directly accessing the registers. The CMSIS version I already gave you in the mail (that you didn't read?) was:
int pressed = GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_0) == 1;