function processData(input) {
    input = input.split(' ').map(Number);
    var a = 0.5*input[0]*input[2];
    var b = 0.5*input[1]*input[2];
    var moduloCrazy = Math.pow(10, 9) + 7;
    console.log((a + b) % moduloCrazy);
} 

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

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