#P5257. Sum of Pairwise Products in a Digit Sum Constrained Set
Sum of Pairwise Products in a Digit Sum Constrained Set
Sum of Pairwise Products in a Digit Sum Constrained Set
Consider a decimal integer \(N = \overline{n_1 n_2 \dots n_m}\) with \(m\) digits. We define \(g(N)=\sum_{i=1}^{m} n_i\). For a given positive integer \(n\), define the set
[ S_n = { x \mid x > 0,; g(x) \le n, ; \text{and every digit in the decimal representation of }x \text{ is nonzero} } ]
We then define
[ f(n)=\sum_{\substack{x,y \in S_n \ x<y}} x \times y \quad (\bmod; 10^6+3). ]
</p>Your task is to compute \(f(n)\) modulo \(10^6+3\) given \(n\).
Hint: Notice that the double summation can be transformed using the identity:
[ \sum_{x<y} x\times y = \frac{1}{2}\Biggl[\Bigl(\sum_{x\in S_n} x\Bigr)^2-\sum_{x\in S_n}x^2\Biggr]. ]
</p>inputFormat
The input consists of a single integer \(n\) (\(1 \le n\le \) [constraint as appropriate]) on one line.
outputFormat
Output a single integer which is the value of \(f(n)\) modulo \(10^6+3\).
sample
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