题目
题意定义奇妙数x 为，存在两个正整数b>a,x = b * b - a * a 求第n个奇妙数，1 all odd numbers are avaiable.(expect for 1) case 2: b and a have the same parity. ---> all numbers, which modulos 4 is 0, is available(expect for 4) x = 2 * k + 1, k >= 1 x = 4 * k, k >= 1 3, 5, 7, 8, 9, 11, 12 2 * 2 - 1 * 1 = 3, 3 * 3 - 2 * 2 = 5, 4 * 4 - 3 * 3 = 7, 3 * 3 - 1 * 1 = 8 */ ll n, m, res; int mp[] = {0, 1, 3}; void solve() { scanf("%lld", &n); if (n == 1LL) { res = 3; } else { n -= 1; res = 4LL + 4 * (n / 3); n %= 3; res += mp[n]; } printf("%lld\n", res); } int main() { int t; // scanf("%d", &t); t = 1; while (t--) { solve(); } }
