设有n种不同面值a1, a2,…, an的邮票，规定每封信最多贴m张邮票。对于给定的m，n，求出最大的邮资连续区间。-With a face value of n different types a1, a2, ..., an of the stamps, each letter provides a maximum of m stamps affixed. For a given m, n, obtained the largest continuous interval of postage