function Main(input){
  input = input.split(" ");
  var a = parseInt(input[0],10);
  var b = parseInt(input[1],10);
  var t = parseInt(input[2],10);
  var sum = 0;
  
  while(b<t+0.5){
        sum += a;
        b = b+b;
}
  console.log(sum);
}
Main(require("fs").readFileSync("/dev/stdin","utf-8"));