function Main(input) {
    var A = parseInt(input[0], 10);
    var B = parseInt(input[1], 10);
 
    var sum = A + B;
 
    console.log(sum % 2 === 0 ? sum/2 : sum/2 + 0.5);
}
 
Main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split(/\n|\s/));