View Compilation Error

0_0_35418462_22451.cpp: In function 'int main()':
0_0_35418462_22451.cpp:7:26: error: 'A' was not declared in this scope
   if(a>=90&&a<=100)cout<<A<<endl;
                          ^
0_0_35418462_22451.cpp:8:29: error: 'B' was not declared in this scope
   else if(a>=80&&a<90)cout<<B<<endl;
                             ^
0_0_35418462_22451.cpp:9:29: error: 'C' was not declared in this scope
   else if(a>=70&&a<80)cout<<C<<endl;
                             ^
0_0_35418462_22451.cpp:10:29: error: 'D' was not declared in this scope
   else if(a>=60&&a<70)cout<<D<<endl;
                             ^
0_0_35418462_22451.cpp:11:14: error: 'E' was not declared in this scope
   else cout<<E<<endl;
              ^