import re

def f(x):
    return ''.join(str(c) for c in range(1,x+1))
print(f":::{f(13)}")

def test(s):
    print("--")
    for x in range(2,8):
        for c in ['2','3']:
            for z in re.finditer(rf"[^{c}][{c}]{{{x}}}[^{c}]",s):
                n=z.start()+1
                print(f"{c*x:>6s} at {n:<6}  [{s[n-8:n+8+x]}]")
                break
            else:
                print(f"{c*x:>6s} none")

test(f(1000000))