#!/usr/bin/env python3

import functools


def compute(ps):
    m = functools.reduce(lambda x, y: x * y % 9, ps) % 9
    return 9 if m == 0 and all(p != 0 for p in ps) else m


def main():
    _ = int(input())
    ps = [int(p) for p in input().split()]
    c = compute(ps)
    print(c)


if __name__ == "__main__":
    main()