费马小定理验证：寻找最小反例

#include \nusing namespace std;\n\nbool isPrime(long long n) {\n if (n <= 1) {\n return false;\n }\n for (long long i = 2; i * i <= n; i++) {\n if (n % i == 0) {\n return false;\n }\n }\n return true;\n}\n\nint main() {\n long long n = 1;\n while (true) {\n if (!isPrime(n * n + 1)) {\n cout << n << endl;\n break;\n }\n n++;\n }\n return 0;\n}