function Main(input){
  ver input = input.split(' ');
  ver U =　new Number(input[0]);
  ver S = new Number(input[1]);
  
　if(U > 9 || S > 9){
   console.log('-1');
 }else if{
   console.log(U * S);
   
   Main(require("fs").readFileSync("/dev/stdin", "utf8"));