Extract and Modify Field in a 32-bit Register

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

uint32_t update_register(uint32_t reg) {
    // Your logic here
    union {
        struct {
            uint32_t lower : 10;
            uint32_t exact : 5;
            uint32_t upper : 17;
        };
        uint32_t val;
    } unBit;
    unBit.val = reg;
    if(unBit.exact < 31)
        unBit.exact++;
    return unBit.val;
}

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