The Female Ghost Wants Me to Do Math Problems or She Will Kill Me

Xia Feng encountered a ghost, but this ghost was different from the one he imagined... Imaginary plot: Person: "Please, I have no enmity with you, please don't kill me!" Ghost: "Everyone... Must die." What happened to Xia Feng: Xia Feng: "I have no enmity with you, can you not kill me?" The female ghost covered in blood said: "Okay, as long as you answer me one question." Xia Feng: "What's the problem?" Female ghost: "It is known that the straight line y=x+1 is tangent to the curve y=lnx+a, then the value of a is _____?" Xia Feng: "..." This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.