Find all additive inverse pairs in Zn

//Find the additive inverse of Zn
#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
    int n;
    while(cin>>n){
        puts("(0, 0)");
        for(int i=0;i<=n/2;i++)
            for(int j=n-1;j>=0;j--)
                if(i+j==n)
                    cout<<"("<<i<<", "<<j<<")"<<endl;
    }
    return 0;
}