BC155 牛牛的素数和

思路：

step1：找到素数，创建计数器，累加打印；

代码如下：

def fn(m,n):
    count = 0
    for i in range(m,n+1):
        x = 2
        flag = True
        while x <= i**0.5 + 1:
            if i != 2 and i%x == 0:
                flag = False
            elif i == 2:
                flag = True
            x += 1
        if flag:
            count += i 
    print(count)
m,n = list(map(int,input().split()))
fn(m,n)