function processData(input) {
    //*****************
    // Define variables
    //*****************
    var inputs = input.trim().replace(/\s+/g, " ").split(" ").map(Number),
        numberOfCells = 1,
        firstGrowthFactor = inputs[0],
        secondGrowthFactor = inputs[1],
        numberOfMilliseconds = inputs[2],
        resultingCells = 0;
    
    //********************
    // Perform calculation
    //********************
        resultingCells = 0.5*firstGrowthFactor*numberOfMilliseconds + 0.5*secondGrowthFactor*numberOfMilliseconds
        resultingCells = resultingCells % (Math.pow(10,9) + 7);
    
    //***************
    // Print solution
    //***************
    console.log(resultingCells);
} 

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

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