Extract Even Bits Only from 32-bit Register

Code

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

uint32_t extract_even_bits(uint32_t reg) 
{
    unsigned int num=0;
    for(int i=31,j=15;i>=0;i--)
    {
        if(i==0)
        {
            if(((reg>>i)&1)==1)
            {
                num |=(1<<j);
                j--;
            }
            else
            {
                num &=~(1<<j);
                j--;
            }
        }
        else if(i%2==0)
        {
           if(((reg>>i)&1)==1)
            {
                num |=(1<<j);
                j--;
            }
            else
            {
                num &=~(1<<j);
                j--;
            }
        }
    }
    return num;
}

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

Solving Approach