22. Extract Even Bits Only from 32-bit Register

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

uint32_t extract_even_bits(uint32_t reg) {
    uint8_t pos = 0;
    uint32_t ret = 0;
    while (reg) {
        if (reg & 0x1)
            ret |= (0x1 << pos);
        reg >>= 2;
        pos++;
    }
    return ret;
}

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