1 //0MS    228K    635 B    C++
 2 #include<stdio.h>
 3 #define N 1005
 4 struct node{
 5     int x,y;
 6 }p[N];
 7 int fun(node a,node b,node c)
 8 {
 9     return (b.x-a.x)*(c.y-b.y)-(c.x-b.x)*(b.y-a.y);
10 }
11 int main(void)
12 {
13     int n;
14     while(scanf("%d",&n)!=EOF && n)
15     {
16         for(int i=0;i<n;i++)
17             scanf("%d%d",&p[i].x,&p[i].y);
18         if(n<3){
19             puts("concave");continue;
20         }
21         int flag=1;
22         for(int i=0;i<n;i++)
23             if(fun(p[i],p[(i+1)%n],p[(i+2)%n])<0){
24                 flag=0;
25                 break;
26             }
27         if(flag) puts("convex");
28         else puts("concave");
29     }
30     return 0;
31 }