var side1=prompt("Inter a:") ;
 var side2=prompt("Inter b:") ;
 var side3=prompt("Inter c:") ;
 var sideA=Number(side1) ;
 var sideB=Number(side2) ;
 var sideC=Number(side3) ;

 if (sideA<sideB+sideC && sideB<sideA+sideC && sideC<sideA+sideB) {
     alert("The shape is a triangle.")
 } else {
     alert("The shape is not a triangle.")
 } ;