#5x + 3y + z/3 = 100
#x + y + z = 100
#hence 7x + 4y = 100
#in range 0<=x<=20, 0<=y<34
#range 0<=x<=14, 0<=y<=25
for x in range(0,15):
    if (100 - 7*x) % 4 == 0:
        y = (100-7*x)//4
        z = 100-x-y
        if z >= 0 and z % 3 == 0:
            print(x,y,z)

14*7 = 98, 所以公鸡数量范围就是0到14，剩下就是判断是否整除。