Write a function that takes a string as an argument and returns the left most digit in the string.
leftDigit("TrAdE2W1n95!") ➞ 2 leftDigit("V3r1ta$") ➞ 3 leftDigit("U//DertHe1nflu3nC3") ➞ 1 leftDigit("J@v@5cR1PT") ➞ 5