View Compilation Error

0_0_33229620_6890.cpp: In function 'int main()':
0_0_33229620_6890.cpp:7:16: error: 'a' was not declared in this scope
     while(cin>>a>>b)
                ^
0_0_33229620_6890.cpp:7:19: error: 'b' was not declared in this scope
     while(cin>>a>>b)
                   ^
0_0_33229620_6890.cpp:18:26: error: 'sort' was not declared in this scope
         sort(a+1,a+len1-1);
                          ^