View Compilation Error

0_0_38891877_4363.cpp:1:14: error: 'M' was not declared in this scope
    1 | int a ,b,n,j[M],i;
      |              ^
0_0_38891877_4363.cpp:5:6: error: expected constructor, destructor, or type conversion before '(' token
    5 | scanf("%d",&n);
      |      ^
0_0_38891877_4363.cpp:7:1: error: expected unqualified-id before 'for'
    7 | for(i=0;i<n;i++)
      | ^~~
0_0_38891877_4363.cpp:7:9: error: 'i' does not name a type
    7 | for(i=0;i<n;i++)
      |         ^
0_0_38891877_4363.cpp:7:13: error: 'i' does not name a type
    7 | for(i=0;i<n;i++)
      |             ^
0_0_38891877_4363.cpp:19:1: error: 'i' does not name a type
   19 | i=0;
      | ^
0_0_38891877_4363.cpp:21:1: error: expected unqualified-id before 'while'
   21 | while(i<n)
      | ^~~~~