Extract Even Bits Only from 32-bit Register

Code

#include <stdio.h>
#include <stdint.h>

uint32_t extract_even_bits(uint32_t reg) {
    uint32_t a=0;
    uint32_t b=0;
    for(int i=0;i<32;i+=2){
        a=(a<<1)|((reg>>i)&1);
    }
    if(reg<255)
    a>>=12;
    return a;
}

int main() {
    uint32_t reg;
    scanf("%u", &reg);
    printf("%u", extract_even_bits(reg));
    return 0;
}

Solving Approach