Output of ++*p++

Can anyone explain me the output.

#include<stdio.h>
int main() {
    int a[]={10,20,30};
    int *p=a;
    ++*p++;
    printf("%d  %d  %d  %d",*p,a[0],a[1],a[2]);
}

output is 20 11 20 30

Postfix incrementation has a higher precedence, so value of second index should have been incremented. Why is the value of first index incremented?

via Chebli Mohamed