function Example(){
   const [a,setA] = React.useState(0);
   const [b,setB] = React.useState(0);
   const [c,setC] = React.useState(0);
   const m = React.useMemo(
      () => {
         console.log(a,b,c);
        return (a+b+c);
     }, [b,c]
   )
   return (<React.Fragment>
                 <button onClick={()=>setA(a+1)}>{m}</button>
                 <button onClick={()=>setB(b+1)}>{b}</button>
              </React.Fragment>);}ReactDOM.render(<Example/>,document.querySelector("div"));