/in/foo.cc: In function 'int main()':
/in/foo.cc:7:5: error: 'doulb' was not declared in this scope
     doulb X1,Y1,X2,Y2,X3,Y3,p;
     ^~~~~
/in/foo.cc:8:10: error: 'a' was not declared in this scope
     cin>>a>>b>>c;
          ^
/in/foo.cc:8:13: error: 'b' was not declared in this scope
     cin>>a>>b>>c;
             ^
/in/foo.cc:8:16: error: 'c' was not declared in this scope
     cin>>a>>b>>c;
                ^
/in/foo.cc:9:40: error: 'p' was not declared in this scope
     cout<<fixed<<setprecision(2)<<sqrt(p*(p-a)*(p-b)*(p-c));
                                        ^