B'Recently Luba bought a monitor. Monitor is a rectangular matrix of size n xe2 x80 x89 xc3 x97 xe2 x80 x89m. But then she started to notice that some pixels cease to work properly. Luba thinks that the monitor will become broken the first moment when it contains a square k xe2 x80 x89 xc3 x97 xe2 x80 x89k consisting entirely of broken pixels. She knows that q pixels are already broken, and for each of them she knows the moment when it stopped working. Help Luba to determine when the monitor became broken (or tell that it 's still not broken even after all q pixels stopped working). The first line contains four integer numbers n, xe2 x80 x89m, xe2 x80 x89k, xe2 x80 x89q (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n, xe2 x80 x89m xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89500, xe2 x80 x891 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89k xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89min(n, xe2 x80 x89m), xe2 x80 x890 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89q xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xc2 xb7m) -- the length and width of the monitor, the size of a rectangle such that the monitor is broken if there is a broken rectangle with this size, and the number of broken pixels. Each of next q lines contain three integer numbers xi, xe2 x80 x89yi, xe2 x80 x89ti (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89xi xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n, xe2 x80 x891 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89yi xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89m, xe2 x80 x890 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89t xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89109) -- coordinates of i-th broken pixel (its row and column in matrix) and the moment it stopped working. Each pixel is listed at most once. We consider that pixel is already broken at moment ti. Print one number -- the minimum moment the monitor became broken, or "-1" if it 's still not broken after these q pixels stopped working. '...