This was an easy one. Used only 5 minutes of the 15 allowed 
For getting the 1111, first swich off all the buttons, then start from low right corner and always swich on that button that gives you the most close number to the 1111 but NOT over it. When you find it, go to the next one, row by row, right to left.
Sorry my English, I hope you understood.

For getting the 1111, first swich off all the buttons, then start from low right corner and always swich on that button that gives you the most close number to the 1111 but NOT over it. When you find it, go to the next one, row by row, right to left.
Sorry my English, I hope you understood.
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