The problem requires us to find the n-th digit in an infinite sequence formed by concatenating all positive integers starting from 1.

Observations:

1. The sequence starts as: 123456789101112131415..., and we need to determine the digit at position (n).

2. A simple way to construct the sequence is to append numbers as strings until we reach the required length.

   Approach:

• Initialize an empty string sequence.
• Iterate from 1 onwards, converting each number to a string and appending it to sequence.
• Stop when sequence reaches at least n characters.

• Print the n-th digit (adjusting for 0-based indexing).

  Complexity Analysis:

  Since numbers grow in length, the loop runs approximately O(sqrt{n}) times, making the approach efficient.

n = int(input())
sequence = ""
for num in range(1, 1000):
    sequence += str(num)
    if len(sequence) >= n:  # You can stop early when sequence is long enough
        break
print(sequence[n - 1])