The operational amplifier having the higher input potential will attempt to equalize its noninverting and inverting inputs by reducing current through resistor R5, but will fail to do so, since {TAIL ~ the diode} connected to the operational amplifier with the higher input signal will become reversed biased and turn off, thereby blocking {HEAD ~ the output} of that operational amplifier 
The operational amplifier having the higher input potential will attempt to equalize its noninverting and inverting inputs by reducing current through resistor R5 , but will fail to do so , since { TAIL ~ the diode } connected to the operational amplifier with the higher input signal will become reversed biased and turn off , thereby blocking { HEAD ~ the output } of that operational amplifier
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