/in/foo.cc: In function 'int main()':
/in/foo.cc:7:10: error: 'b' was not declared in this scope
  cin>>a>>b>>m>>n;
          ^
/in/foo.cc:10:3: error: expected primary-expression before '=' token
   =a+b;
   ^
/in/foo.cc:13:5: error: 'c' was not declared in this scope
   b=c;
     ^
/in/foo.cc:5:8: warning: unused variable 'bc' [-Wunused-variable]
  int a,bc,m,n;
        ^~