#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<algorithm>
#include<cstdlib>
#include<queue>
#include<vector>
#include<set>
using namespace std;
int n,x[1010],y[1010];
bool flag;
int main()
{
      while(scanf("%d",&n)!=EOF)
      {
            flag=false;
            if(n==0) break;
            for(int i=0;i<n;i++)
                  scanf("%d%d",&x[i],&y[i]);
            x[n]=x[0],y[n]=y[0],x[n+1]=x[1],y[n+1]=y[1];
            for(int i=0;i<n;i++)
            {
                 if(((x[i]-x[i+1])*(y[i+1]-y[i+2])-(y[i]-y[i+1])*(x[i+1]-x[i+2]))<0)
                 {
                       flag=true;
                       break;
                 }
            }
                 if(flag)
                        printf("concave\n");
                 else
                        printf("convex\n");
      }
      return 0;
}