Extract and Modify Field in a 32-bit Register

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

uint32_t update_register(uint32_t reg) {
    uint8_t mask = 1;
    mask = (mask << 5) - 1;
    mask &= reg >> 10;
    if (mask>=31) return reg;
    else mask++;
    reg &= ~(((1U << 5) - 1) << 10);
    reg |= mask << 10;
    return reg;
}

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