realloc() : invalid pointer ?

[creeping death]

i m trying to understand dynamic memory allocation.

this is what i tried...and failed at

#include<stdio.h>
#include<stdlib.h>
int main()
{
    int *start,*values,i;

/*hmm...i dunno lets allocate 20 integer size block, to be on the safe side*/

    values=(int *) malloc(20 * sizeof(int));
    start=values;

    printf(" add(start)=&#37;u, add(value)=%u\n",start,values);
    printf("Enter the values(0 to stop)\n");
    for(i=0 ; i<10 ; i++)
    {
        scanf("%d",values); 
        printf("\tvalue(value)=%d\tadd(value)=%u\t",*values,values);  
        values++;
    }
/* well, only 10 integers were stored! looks like i allocated more earlier, lets reduce the size :) */

    values =(int *) realloc(values,10 * sizeof(int));

    values=start;
    for(i=0 ; i<20 ; i++)
    {
        printf("%d\t%u\n",*values,values);
        values++;
    }
     return 0;
}

there are no errors or warnings in compilation
when i run the program, the first half of program(taking in values) executes. after i enter the 10th number.

i get an error message

*** glibc detected *** ./a.out: realloc(): invalid pointer: 0x081df030 ***
======= Backtrace: =========
/lib/libc.so.6[0x48b3a4]
/lib/libc.so.6(realloc+0x242)[0x48fdc2]
/lib/libc.so.6(realloc+0x42)[0x48fbc2]
./a.out[0x80484f9]
/lib/libc.so.6(__libc_start_main+0xe5)[0x4326e5]
./a.out[0x80483c1]
======= Memory map: ========
00110000-00111000 r-xp 00110000 00:00 0          [vdso]
003f7000-00417000 r-xp 00000000 08:02 805385327  /lib/ld-2.9.so
00418000-00419000 r--p 00020000 08:02 805385327  /lib/ld-2.9.so
00419000-0041a000 rw-p 00021000 08:02 805385327  /lib/ld-2.9.so
0041c000-0058a000 r-xp 00000000 08:02 808903508  /lib/libc-2.9.so
0058a000-0058c000 r--p 0016e000 08:02 808903508  /lib/libc-2.9.so
0058c000-0058d000 rw-p 00170000 08:02 808903508  /lib/libc-2.9.so
0058d000-00590000 rw-p 0058d000 00:00 0 
00a6c000-00a79000 r-xp 00000000 08:02 808904130  /lib/libgcc_s-4.3.2-20081105.so.1
00a79000-00a7a000 rw-p 0000c000 08:02 808904130  /lib/libgcc_s-4.3.2-20081105.so.1
08048000-08049000 r-xp 00000000 08:02 809327092  /home/c_d/workspace/Info Security/RSA/a.out
08049000-0804a000 rw-p 00000000 08:02 809327092  /home/c_d/workspace/Info Security/RSA/a.out
081df000-08200000 rw-p 081df000 00:00 0          [heap]
b7f8a000-b7f8b000 rw-p b7f8a000 00:00 0 
b7fae000-b7fb1000 rw-p b7fae000 00:00 0 
bfb9c000-bfbb1000 rw-p bffeb000 00:00 0          [stack]
	1	136179756	Aborted

isnt this how one is supposed to use realloc() ?
what am i doing wrong here?