#include using namespace std; //判断是不是质数 bool isPrime(int n) { //最快的方法 if (n < 2) return false; if (n == 2 || n == 3) return true; if (n % 6 != 1 && n % 6 != 5) return false; for (int i = 5; i <= floor(sqrt(n)); i += 6) if (n % i == 0 || n % (i + 2) == 0) return false; return true; } int main() { int n; cin >> n; //1、找到所有比当前数小的质数 int a[100] = {0}; int k = 0; for (int i = 2; i <= n; ++i) { if (isPrime(i)) { a[k++] = i; } } //2、两两配对,是不是加在一起等于当前数 bool found = false; for (int i = 0; i < k; ++i) { for (int j = 1; j <= k; ++j) { if (a[i] + a[j] == n) { cout << n << "=" << a[i] << "+" << a[j] << endl; found = true; break; } } if (found) break; } return 0; }