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

#define MAX_LENGTH 10

struct Arr {
    int length;
    int data[];
};

int main() {
    struct Arr * arr = malloc(sizeof(struct Arr) + MAX_LENGTH);
    
    arr->length = 10;
    arr->data[0] = 1;
    arr->data[100] = 3;
    printf("%d\n", arr->data[100]);
    
    free(arr);
    
    printf("Hello world!\n");
    return 0;
}