Add Signed and Unsigned Integers Safely

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

int16_t signed_unsigned_sum(int8_t a, uint8_t b) {
    int16_t Ar = (a > 127) ? (int16_t)(~a + 1) : (int16_t) a;
    return Ar + (int16_t)b;
}

int main() {
    int8_t a;
    uint8_t b;
    scanf("%hhd %hhu", &a, &b);
    printf("%d", signed_unsigned_sum(a, b));
    return 0;
}