pt13 根据叶子判断四季

if (leaf.color==green)    
spring comes;

if (leaf.temperture>=36℃)    
summer comes;

if (leaf.color==yellow)    
autumn comes;

only (
leaf_1 is hanging on a tree &&
leaf_2 is dancing in the wind &&
leaf_3 is lying on the grass &&
leaf_4 is sleeping near a garbage bin &&
…
leaf_n is shivering and getting cold)
then    winter comes;