Solving Linear Congruences.sagews

ModSolver finds a solution of the equation a* x = b mod n

def ModSolver(a,b,n):
    testxgcd = xgcd(a,n)
    if testxgcd[0]!=1:
        print "a and n are not coprime"
        return None
    ainv = testxgcd[1]
    return (ainv*b)%n
A=3687643928749827493284733847932849326478268265438567836493287498237498327493273684983729400073294873001
B=4356483636578364578346584638564385643875643856478365874365874365834001
N=3246387264832647832643924793287439827493827493287498327492374036483684362803428768326583653457347325473254730001
X=ModSolver(A,B,N)
X 

3193344696006285988199840326650376758798369858174091258235893436186808593260532708688549688263925514745711729468

A*X %N
B

4356483636578364578346584638564385643875643856478365874365874365834001 4356483636578364578346584638564385643875643856478365874365874365834001

xgcd(71,73)

(1, 36, -35)