How can this printf statement be executed by the C compiler?

Question

I am confused about how the printf statement is working in this program? I want to know the way of executing.

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

int main()
{
    int a=5;
    printf("%d %d %d %d\n",a++,++a,++a,1);
    printf("%d",a);
    //printf("Hello world!\n");
    return 0;
}

Answer 1

This will invoke undefined behavior. Statement

 printf("%d %d %d %d\n",a++,++a,++a,1);  

trying to modify a thrice between two sequence point.