View Compilation Error

0_0_29902021_9787.cpp: In function 'int main()':
0_0_29902021_9787.cpp:28:14: error: 'len' was not declared in this scope
     sort(b,b+len,cmp);
              ^
0_0_29902021_9787.cpp:32:7: error: 'flag' was not declared in this scope
       flag = 1;
       ^
0_0_29902021_9787.cpp:36:8: error: 'flag' was not declared in this scope
     if(flag == 0)
        ^
0_0_29902021_9787.cpp: At global scope:
0_0_29902021_9787.cpp:41:1: error: expected declaration before '}' token
 } 
 ^