operator int()

SomeClass{
               public:
                       int i;
                       SomeClass(int j):i(j){};
                       operator int(){
                                       return this->i;
                       }
              // some functions (all of them public) and
constructors ??

};
int main(void){
           SomeClass s(10);
           int i=s;
           cout<<i<<endl;
           return 0;
}

I am not able to understand why this is printing 10 ??? How is
"operator int()" function called ??