Bubble Sort - Time Complexity

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
 
int main()
{
    int i, j, a[300000], num, temp;
    double start, end;
    srand(time(0));
    printf("Enter input size: ");
    scanf("%d", &num);
    printf("\nInput Array: ");
    for(i = 0; i < num; i++)
    {
        a[i] = rand()%1000;
        printf("%d ", a[i]);
    }
    start = clock();
    for(i = 0; i < num; i++)
    {
        for(j = 0; j < num-i-1; j++)
        {
            if(a[j] > a[j+1])
            {
                temp = a[j];
                a[j] = a[j+1];
                a[j+1] = temp;
            }
        }
    }
    end = clock();
    printf("\n\nSort: ");
    for(i = 0; i < num; i++)
    {
        printf("%d ", a[i]);
    }
 
    printf("\n\nExecution time: %.3lf s\n\n", (end-start)/1000);
}