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Kosovo Mathematical Olympiad 2016 TST , Problem 4

Source:

January 9, 2017
functional equation

Problem Statement

It is given the function f:RRf:\mathbb{R}\rightarrow \mathbb{R} fow which f(1)=1f(1)=1 and for all xRx\in\mathbb{R} satisfied
f(x+5)f(x)+5f(x+5)\geq f(x)+5 and f(x+1)f(x)+1f(x+1)\leq f(x)+1
If g(x)=f(x)x+1g(x)=f(x)-x+1 then find g(2016)g(2016) .