  Issai Schur once asked if it was possible to determine a bound, preferably
using elementary methods, such that for all prime numbers p greater than the
bound, the greatest number of consecutive quadratic non-residues modulo p is
always less than the square root of p. This paper uses elementary methods to
prove that 13 is the only prime number for which the greatest number of
consecutive quadratic non-residues modulo p exceeds the square root of p.
