foo.c:6:7: warning: return type of 'main' is not 'int' [-Wmain]
    6 | }void main(){int x,a,b,c;
      |       ^~~~
foo.c:6:7: error: conflicting types for 'main'; have 'void()'
foo.c:3:5: note: previous definition of 'main' with type 'int()'
    3 | int main()
      |     ^~~~
foo.c: In function 'main':
foo.c:8:1: error: 'cin' undeclared (first use in this function)
    8 | cin>>x;a=x/100;
      | ^~~
foo.c:8:1: note: each undeclared identifier is reported only once for each function it appears in
foo.c:12:1: error: 'cout' undeclared (first use in this function)
   12 | cout<<c*100+b*10+a<<endl;
      | ^~~~
foo.c:12:21: error: 'endl' undeclared (first use in this function)
   12 | cout<<c*100+b*10+a<<endl;
      |                     ^~~~
foo.c:12:1: error: expected declaration or statement at end of input
   12 | cout<<c*100+b*10+a<<endl;
      | ^~~~

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