function processData(input) {
    var array = input.split(" "); 
    var totalSquares = array[0] * array[1];
    var totalCuts = 0;
    if (array[0]==1 || array[1]==1){
            totalCuts = (totalSquares-1); 
    }
    if (array[0]>=2 || array[1]>=2){
            totalCuts = totalSquares-1; 
    }

    process.stdout.write(totalCuts);
        
} 

process.stdin.resume();
process.stdin.setEncoding("ascii");
_input = "";
process.stdin.on("data", function (input) {
    _input += input;
});

process.stdin.on("end", function () {
   processData(_input);
});