ural 1494 Monobilliards

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;

 int a[],b[];
 int main()
 {
     int n;
     while(scanf("%d",&n)!=EOF)
     {
         for(int i=; i<=n; i++)
             scanf("%d",a+i);
         int top=,top1=;
         for(int i=; i<=n; i++)
         {
             b[++top]=i;
             while(top&&b[top]==a[top1]){
                top--;top1++;
             }
         }
         if(top) printf("Cheater\n");
         else printf("Not a proof\n");
     }
     return ;
 }