#!/usf/local/bin/python3

def sum(n, i=1):
    if n <= 0:
        return n
    print(f"count     : {i}回")
    total = n + sum(n-1, i+1)
    print(f"n         : {n}")
    print(f"n-1       : {n-1}")
    print(f"n + (n-1) : {total}")
    return total

print("sum(3) =", sum(3))