a question about how to work with c functions in asm

Hi Guys...!
Look the following source...! please!

.section .data
          data1:
          .int 200000
          data2:
          .int 201010
          result:
          .quad 0
          output:
          .asciz "The result is %qd\n"
.section .text
.globl main
main:
          nop
          movl data, %eax
          mull data2
          movl %eax, result
          movl %edx, result+4
          pushl %edx
          pushl %eax
          call printf
          add $12, %esp
          pushl $0
          call exit
          

Guys i dont know why using add $12, %esp in this snippet code!
Who can tell me what does it instruction in this code?!

sorry for bad english speaking!