#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>

using namespace std;

#define x first
#define y second
typedef long long LL;
typedef pair<int,int> Point;
const int N = 2550;

vector<Point>e;

int main()
{
    int n ,xx, yy ;
    #ifdef LOCAL

        freopen("in.txt","r",stdin);
    #endif
    while(cin>>n)
    {
        if(!n)break;
        e.clear();
        for(int i = 0 ; i< n ;++i ){
            cin>>xx>>yy;
            e.push_back(Point(xx,yy));
        }
        int flag = 1 ;
        for( int i =0 ; i < n  ; ++i ){
            if( ( e[ (i+1) % n  ].x  - e[i].x ) * ( e[(i+2) % n ] .y - e[(i+1) % n].y ) -
               ( e[ (i+1) % n  ].y  - e[i].y ) * ( e[(i+2) % n ] .x - e[(i+1) % n].x ) < 0 ){
                flag = 0 ;
                break ;
            }
        }
        if(flag )
            cout<<"convex"<<endl;
        else
            cout<<"concave"<<endl;
    }
    return  0;
}