checking fermat's theorem

def checkfermat(a,b,c,n):
    try:
        a = int(a)
    except ValueError:
        print "a is not a proper integer"

    try:
        b = int(b)
    except ValueError:
        print "b is not a proper integer"

    try:
        c = int(c)
    except ValueError:
        print "c is not a proper integer"

    try:
        n = int(n)
    except ValueError:
        print "n is not a proper integer"
    print "a**n + b**n = ",a**n + b**n,"c**n is:",c**n
    if a**n + b**n == c**n:
        print "This case proves fermat's theorem wrong!"
    else:
        print "The theory holds."
    supplyargs(a,b,c,n)

def supplyargs(a='4',b='5',c='6',n='3'):
    'supply args for checking fermats theorem'
    print "values are a:",a,"b:",b,"c:",c,"n:",n
    string = raw_input("type a,b,c, or n followed by a dash and the number, or type 'ready':")
    t = string[0]
    if string == "ready":

        checkfermat(a,b,c,n)
    if t != "a" and t != "b" and t != "c" and t != "n" and string != "ready":
        print "Error: the first character was neither a,b,c or n."
        supplyargs(a,b,c,n)
    if string != "ready":
        try:
            t = string[1]
        except IndexError:
            print "The string is not long enough."
            supplyargs(a,b,c,n)
        if t != "-":
            print "Error: the second character was not a dash(-)."
            supplyargs(a,b,c,n)
        else:
            print "running else"
            t1 = string[0]
            t2 = string[2:]
            if t1 == 'a':
                a = t2
            if t1 == 'b':
                b = t2
            if t1 == 'c':
                c = t2
            if t1 == 'n':
                n = t2
            supplyargs(a,b,c,n)

supplyargs()