ffmpeg: video is not creating for uneven pixel ratio images

I am using ffmpeg for create a video using images, its creating video for uniform images (ie all the images should be same pixel ratio). It doesn't work for different pixel ratio images, its missing some images in video I am using this command to create a video in windows

ffmpeg -r 1/5 -i img%03d.jpg -c:v libx264 video.mp4

these are the images and its pixel ratio

img001.jpg 350X250

img002.jpg 1280X768

img003.jpg 1280X768

img004.jpg 720X480

img005.jpg 720X480

img006.jpg 1000X750

Here video is creating for img001.jpg, img002.jpg, img003.jpg and img005.jpg it exludes img004.jpg and img006.jpg

Any command option to create video for all the uneven pixel images ?