Mikaela would use 16 / 4 = <<16/4=4>>4 containers of paint per wall.
To paint 3 walls, she will use 3 * 4 = <<3*4=12>>12 containers.
After using 1 container for the ceiling, she will have 16 - 12 - 1 = <<16-12-1=3>>3 containers of paint left over.
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