View Compilation Error

0_0_37120994_334.cpp: In function 'int main()':
0_0_37120994_334.cpp:6:2: error: expected initializer before 'scanf'
  scanf("%d",&a);
  ^
0_0_37120994_334.cpp:7:2: error: 'b' was not declared in this scope
  b=-a;
  ^
0_0_37120994_334.cpp:10:10: error: expected '}' at end of input
  return 0;
          ^