why shift int a=1 to left 31 bits then to right 31 bits, it becomes -1

Question

given

int a = 1; (00000000000000000000000000000001),

what I did is just

a=(a<<31)>>31;

Answer 1

" however it turns out to be -1"

You use an unsigned int to do so for seeing only 32 bit values that are greater than 0:

 unsigned int a = 1; 
 a=(a<<31)>>31;