def SUM(n):
    ans=0
    while n:
        ans+=n%10
        n/=10
    return ans



def main():
    n=int(raw_input())
    n/=2

    m={}

    for i in range(0,10**n):
        try:
            m[SUM(i)]+=1
        except:
            m[SUM(i)]=1
    ans=0

    for i in m:
        ans+=m[i]*(m[i])
        #print i, m[i]
    print ans
main()

I used dictionary ( in c/c++ it's map)

Edited by author 25.07.2014 18:56

Edited by author 25.07.2014 18:57