求出指定区所有能被3和5整除的整数之和并展现求和过程

请问如何修改才能使实现
m＝100
n＝150
s＝105＋120＋135＋150＝510

是这样吗？仅供参考

m = int(input("m:"))
n = int(input("n:"))

sum1 = 0
str1 = ""
for item in range(m, n+1):
    if item % 3 == 0 and item % 5 == 0:
        str1 += str(item) + "+"
        sum1 += item
print("\n")
print(f"m={m}")
print(f'n={n}')
print(f"{str1[0:-1]}={sum1}")