Error in: orb_slam2_mod

[hesamira]

Hi,
I have faced with the following errors.
Please, guide me.
Thanks.

sami@sami-Vostro-1520:~/orb_slam2_mod/src/orb_slam2_mod$ ./build.sh  

/home/sami/orb_slam2_mod/src/orb_slam2_mod/src/System.cc:332:20: error: 'usleep' was not declared in this scope usleep(5000);

[AnGPU]

There was the same error with the original orbslam2:
find that file,and add the following codes to it:

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