#include <bits/stdc++.h>

using namespace std;
ifstream in("sume.in");
ofstream out("sume.out");
int main(){
   int p;
   in>>p;
   int c=p;
   c*=2;
   c=sqrt(c);
   /*if(c*(c+1)/2==p){
        out<<c+1<<"\n";
        vector<int> v;
        for(int i=0;i<=c;i++){
            int nr;
            in>>nr;
            v.push_back(nr);
        }

        int a=v[0]+v[1]-v[c];
        a/=2;
        out<<a<<" ";
        v.pop_back();
        for(auto i:v){
            out<<i-a<<" ";
        }
   }else{
    out<<-1;
   }*/
   out<<-1;
}