var input = '';
process.stdin.resume();
process.stdin.setEncoding('utf8');
process.stdin.on('data', function (chunk) {
    input += chunk;
});
process.stdin.on('end', function () {
    input = input.split('\n');
    main();
});


function main() {
    var first_line=input[0].split(" ").map(function (x) {
        return x-0;
    });
    console.log(
        50*first_line[0]+Math.floor((50*first_line[0]/(8+2*first_line[1])*10))
    );
}

/**
 * Created by Administrator on 2016/11/25 0025.
 */