View Compilation Error

0_0_28519275_16123.cpp: In function 'int main()':
0_0_28519275_16123.cpp:9:22: error: 'L' was not declared in this scope
  while(scanf("%d%d",&L,&n)!=EOF){
                      ^
0_0_28519275_16123.cpp:9:25: error: 'n' was not declared in this scope
  while(scanf("%d%d",&L,&n)!=EOF){
                         ^
0_0_28519275_16123.cpp:11:16: error: 'length' was not declared in this scope
    scanf("%d",&length[i]);
                ^
0_0_28519275_16123.cpp:15:8: error: 'length' was not declared in this scope
   sort(length,length+n,cmp);
        ^
0_0_28519275_16123.cpp:15:24: error: 'cmp' was not declared in this scope
   sort(length,length+n,cmp);
                        ^