https://www.acmicpc.net/problem/14954 14954번: Happy Number Your program is to read from standard input. The input consists of a single line that contains an integer, n (1 ≤ n ≤ 1,000,000,000) www.acmicpc.net 문제 Consider the following function f defined for any natural number n: f(n) is the number obtained by summing up the squares of the digits of n in decimal (or base-ten). If n = 19, for examp..