#include <iostream>
#include<vector>
using namespace std;
int main() {
// your code goes here
vector<int> a={1,3,4,5,2,7,8};
vector<int> f;
int k=7;
for(int i=0;i<a.size();i++) {
for(int j=i+1;j<a.size();j++) {
if(abs(a[i]-a[j])==k) {
cout<<a[i]<<a[j]<<endl;
}
}
}
return 0;
}
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