View Compilation Error

0_0_29407055_3794.cpp: In function 'int main()':
0_0_29407055_3794.cpp:40:12: error: 'A' was not declared in this scope
   if(x[0]>=A&&x[0]<=Z)
            ^
0_0_29407055_3794.cpp:40:21: error: 'Z' was not declared in this scope
   if(x[0]>=A&&x[0]<=Z)
                     ^
0_0_29407055_3794.cpp:42:21: error: 'A' was not declared in this scope
   if(x[x.size()-1]>=A&&x[x.size()-1]<=Z)
                     ^
0_0_29407055_3794.cpp:42:39: error: 'Z' was not declared in this scope
   if(x[x.size()-1]>=A&&x[x.size()-1]<=Z)
                                       ^