Set Multiple Bits in 8-bit Register

Code

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

uint8_t set_range(uint8_t reg, uint8_t start, uint8_t end) {
    int len = end - start + 1;
    int val = 0;
    for(int i = 0; i < len; i++){
        val += pow(2, i);
    }
    reg |= (val << start);

    return reg;
}

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

Solving Approach