#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

int round_down(int n, int multiple_of) {
    int n_rounded_down = (n * multiple_of) / multiple_of;    // BUG!!!
    return n_rounded_down;

    //int n_rounded_down = (n / multiple_of) * multiple_of;  // CORRECT
}

int main(int argc, char* argv[]) {
    int n = 7;
    int divisor = 3;
    int n_rounded_down = round_down(n, divisor);

    printf("round_down(7, 3) == %d\n", n_rounded_down); // → 6

    return EXIT_SUCCESS;
}

//  // Enforce that the returned value must be an even multiple of 'multiple_of'.
//  assert(n_rounded_down % multiple_of == 0);
//  // If this is not true, it will deliberately crash our program.

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