this is the excel formula to calculate it

=ROUND(LN(D3)/-LN((1-E3)),0)
where D3 holds the sample size and E3 is the probability.

so if you had 1000 bets your longest run of outs (ROOTS) could be as high as 79
for 5000= 97 and 10000= 105.
even in your first 500 you could expect ROOTS of 71 and in the first 100 - 52 ROOTS

so if your bank wasn't big enough you could be ROOTED by the ROOTS