Here is a C language program. On a machine with 8 8-bit byte long longs, what is the answer?

Here is a C language program. On a twos-complement machine with 8 8-bit byte long longs, what is the answer?

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#include <stdio.h>

int main(int argc, char** argv) {
    unsigned long long value = -1;
    int counter = 0;
    while(value) {
        ++counter;
        value &= value-1;
    }
    printf("%d\n",counter);
    return 0;
}

This can be done easily without actually running the program. I have had it presented to me on job interviews without a computer to run it on available. I did answer correctly.

This code was ran as-is in the Brilliant coding environment. It computed the correct answer.