백준 1292번 [Python] - 쉽게 푸는 문제

a,b=map(int,input().split())
list=[]
 
def koo(x):
    global list
    for i in range(x):
        list.append(x)
    return
 
for i in range(b+1):
    koo(i)
 
sum=0
for i in range(a,b+1):
    sum+=list[i-1]
    
print(sum)