func anyCommonElements<T: Sequence, U: Sequence>(_ lhs: T, _ rhs: U) -> [T.Iterator.Element]
        where T.Iterator.Element: Equatable, T.Iterator.Element == U.Iterator.Element {
            
            var list: [T.Iterator.Element] = []
            
            print(type(of: list))
            
            for lhsItem in lhs {
                
                for rhsItem in rhs {
                    
                    if lhsItem == rhsItem {
                        
                        list.append(lhsItem)
                        return list
                    }
                }
            }
            
            return list
    }
 
    print(anyCommonElements([1, 2, 3], [3]))
    
    print(anyCommonElements(["guo", "teng", "zhao"], ["zhao"]))