BA

#include <stdio.h>
char stack[200000] = {0};
char buffer[200020] = {0};
int main(){
    int top = -1;
    fgets(buffer,200000,stdin);
    //puts(buffer);
    int cur = 0,flag=0;
    char ch;
    for(;;){
        if(buffer[cur] == '('){
            cur++;
            stack[top++] = '(';
        }
        else if(buffer[cur] == '['){
            cur++;
            stack[top++] = '[';
        }
        else if(buffer[cur] == '{'){
            cur++;
            stack[top++] = '{';
        }
        else if(buffer[cur] == ')'){
            cur++;
            ch = stack[--top];
            if(ch != '('){
                flag = 1;break;
            }
        }
        else if(buffer[cur] == ']'){
            cur++;
            ch = stack[--top];
            if(ch != '['){
                flag = 1;break;
            }
        }
        else if(buffer[cur] == '}'){
            cur++;
            ch = stack[--top];
            if(ch != '{'){
                flag = 1;break;
            }
        }
        else{
            break;
        }
    }
    puts((top == -1 && !flag)?"AC":"CE");
    return 0;
}