3218.sagews

def exGCD (m, n):  
    if n==0: 
        d = m 
        x = 1 
        y = 0 
        return(d,x,y)
    else:
        x2=1
        x1=0
        y2=0
        y1=1     
        while n>0: 
            q = m//n
            r=m-q*n
            x=x2-q*x1 
            y=y2-q*y1 
            m=n
            n=r
            x2=x1
            x1=x
            y2=y1
            y1=y
            d=m
            x=x2
            y=y2
        return(d,x,y)
exGCD (3, 7)

(1, -2, 1)