摘要：
Problem Description A group of explorers has found a solitary island. They land on the island and explore it along a straight line. They build a lot o 阅读全文
摘要：
题面 "传送门" 分析 引理1:三角形的面积$\times 2$一定是整数 由坐标系中的三角形面积公式 $$S=\frac{1}{2}(x_1y_2+x_2y_3+x_3y_1 x_1y_3 x_2y_1 x_3y_2)$$ 显然得证 故若$\frac{2nm}{k}$是整数,则有解,否则无解 引理 阅读全文