For every natural *n*, let *X*(*n*) be the smallest natural *m*
such that *m* ends with *n* and *m* is a multiple of 7.
For instance,
*X*(1) = 21,
*X*(2) = 42,
*X*(3) = 63,
…,
*X*(7) = 7,
*X*(8) = 28,
*X*(9) = 49,
*X*(10) = 210,
*X*(11) = 511,
…Let *S* be the infinite concatenation of *X*(*i*) for every *i* ≥ 1,
that is, *S* = 21426314355672849210511....
Which is the *i*-th digit of *S*?

**Input**

Input consists of several cases,
each with a natural *i* between 1 and 10^{15}.

**Output**

For every *i*, print the *i*-th digit of *S* (starting at one).

Public test cases

**Input**

1 2 3 4 13 14 15 18 19 20 1000000000000 1000000000000000

**Output**

2 1 4 2 7 2 8 2 1 0 4 5

Information

- Author
- Salvador Roura
- Language
- English
- Official solutions
- C++
- User solutions
- C++
- Event
- Onzè Concurs de Programació de la UPC - Semifinal
- Date
- 2013-06-19