In mathematics, the four color theorem, or the four color map theorem, states that, given any separation of a plane into regions, producing a figure called a "map", no more than four colors are required to color the regions of the map so that no two adjacent regions have the same color. "Adjacent" means that two regions share a common boundary curve segment, not merely a corner where three or more regions meet. It was the first major theorem to be proved using a computer. Initially, this proof was not accepted by all mathematicians because the computer-assisted proof was infeasible for a human to check by hand. Since then the proof has gained wide acceptance, although some doubters remain.