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