Simple. Each input must connect to a 3 input AND gate and also a 3 input OR gate. The output of the AND gate and the output of the OR gate must connect to the inputs of a 2 input XNOR gate. If all inputs are 0 then the outputs of the AND and OR gates are the same being 0. If all inputs are 1 then the outputs of the AND and OR gates are the same being 1. If any input is different to the other inputs then the output of the AND gate will always be 0 and the output of the OR gate will always be 1 and therefore are not the same. If the inputs of the XNOR gate are the same, the output is 1 and if the inputs of the XNOR gate are different, the output is 0!