python等差数列求和的问题

第一天挣50元，第二天挣80元，第三天挣110元…请编写程序，输入n，计算并输出n天挣的工资总额

n = int(input())
sum = 50
for i in range(1, n):
    sum = sum + 50*i + 30
print(sum)

n = eval(input())
start = 50
sum = 0
for i in range(1,n+1):
  sum += start
  start += 30
print(sum)

n = int(input())
print(sum(range(50,50+30*n,30)))