def fusio(s1,s2):
    s3 = ''
    longmin = min(len(s1),len(s2))
    for i in range(longmin):
        if s1[i] == s2[i]:
            s3 = s3 + s1[i]
        else:
            s3 = s3 + s1[i] + s2[i]
    if len(s1)>len(s2):
        s3 = s3 + s1[longmin:]
    elif len(s1)<len(s2):
        s3 = s3 + s2[longmin:]
    return s3