22. Extract Even Bits Only from 32-bit Register

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

uint32_t extract_even_bits(uint32_t reg) {
    int result = 1;
    while (reg)
    {
        if (reg & 1)
            result <<= 1;
        reg >>= 2;
    }
    return result - 1;
}

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