n个石头(每相邻两个的距离是1米,最边上石头和岸的距离也是1米),礼物放在第m个石头上,青蛙第i次跳2*i-1米.问能否得到礼物.(n>=49肯定能得到礼物,n<49,可以bfs或递归)-n stones (each of the two adjacent distance of a meter, the most edge of the rocks and the shore is a distance meters), gifts m on the first stone, th