Stepan and pairs

1 Sekunde

128 Megabyte

Sehr leicht

Stepan is interested in the greatest common divisor of a pair of numbers, namely $GC D (x, y)$ GCD(x, y). Given an integer $n$ , Stepan wants to know how many pairs of integers $(i, j)$ exist such that $1 \leq i, j \leq n$ 1 \le i, j \le n and $i = GC D (i, j)$ i = GCD(i, j).

Eingabe

One integer $n (1 \leq n \leq 1 0^{6})$ n~(1 \le n \le 10^6).

Ausgabe

Print the number of such pairs.

Beispiele

Beispiel 1

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GC D (x, y)

1 \leq i, j \leq n

i = GC D (i, j)

n (1 \leq n \leq 1 0^{6})