What will be the output of the following C++ code?

#include <stdio.h>
int main ()
{
    int n;
    FILE * p;
    char buffer [5];
    p = fopen ("myfile.txt", "w+");
    for ( n = 'A' ; n <= 'D' ; n++)
    fputc ( n, p);
    rewind (p);
    fread (buffer, 1, 5, p);
    fclose (p);
    buffer[3] = '\0';
    puts (buffer);
    return 0;
}