In this lecture we introduce a third paradigm of algorithmic design. Greedy algorithms are based on taking local optimization steps without regard to the global structure of the problem. Naturally, this can't guaranteed optimal solutions. However, for some problems such local choices are fair enough to generate global optimal solution. One such problem we consider in this lecture is the unweighted interval scheduling. The instruction language is Arabic, however, all material, slides, definitions, concepts, examples, equations, are all in English.