According to Mark 14:30 before the rooster crows twice Peter would deny Jesus three times:
Mark 14:30 And Jesus said to him, “Truly, I tell you, this very night, before the rooster crows twice, you will deny me three times."
But in Mark 14:68 the rooster crows the first time after Peter's first denial:
Mark 14:68 But he denied it, saying, “I neither know nor understand what you mean.” And he went out into the gateway and the rooster crowed
Isn't it supposed to be that Peter denies Jesus three times and only then does the rooster crow twice, isn't this therefore a contradiction?