18. Set Multiple Bits in 8-bit Register

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


uint8_t set_range(uint8_t reg, uint8_t start, uint8_t end) {
    if (start > 7 || end > 7 || start > end) return reg; 
    
    uint8_t mask = ((1 << (-start + end + 1))- 1) << start;
    return reg | mask;
}



int main() {
    uint8_t reg, start, end;
    scanf("%hhu %hhu %hhu", &reg, &start, &end);
    printf("%u", set_range(reg, start, end));
    return 0;
}