first题解！

#include<bits/stdc++.h>
using namespace std;
int a,b[3451234],c;
bool s=0;
map<int,int>n;
int main()
{
cin>>a;
for(int i=1;i<=a;i++){
cin>>b[i];
n[b[i]]++;
}
cin>>c;
sort(b+1,b+a+1);

for(int i=1;i<=a;i++){
    int x=b[i];
    int y=c-b[i];
    if(x==y&&n[y]>1){
        cout<<x<<" "<<y<<'\n';
        return 0;
    }else if(x!=y&&n[y]>0){
        cout<<x<<" "<<y<<'\n';
        return 0;
    }
}
cout<<"No";
return 0;

}