题解

#include<bits/stdc++.h>
using namespace std;

bool is_prime(int x)
{
	if (x==2) returnn true;
	if (x==0 || x==1 || x%2==0) return false;
	for (int i=3;i<=sqrt(x);i+=2)
	{
		if (x%i==0) return false;
	}
	return true;
}

int main()
{
    int n,a,b,m;
    cin >> n;
    bool ar[n];
    for (int i=0;i<n;i++)
    	ar[i]=is_prime(i);
    for (int j=4;j<=n;j+=2)
    {
	    for (int i=0;i<j;i++)
	    {
	    	if (ar[i] && ar[j-i])
	    	{
	    		a=i;
	    		b=j-i;
	    		break;
			}
		}
		cout << j << '=' << a << '+' << b << endl;
    }
    return 0;
}