为什么这段代码会出错?
def checkfermat(a,b,c,n) :
if (a**n+b**n)!=c**n :
print "fermat is absolutely correct.."
else :
print "he is wrong"
a=raw_input("enter the first number")
b=raw_input("enter the second num")
c=raw_input("enter the third num")
d=raw_input("enter the fourth num")
checkfermat(a,b,c,d)
没有用户输入部分,它显示没有错误?