'use strict';
const main = input => {
  input = input[0].split(' ').map(val => parseInt(val));
  const a = input[0], b = input[1], x = input[2];
  console.log(Math.atan(a * b * b / 2 / x) * 180 / Math.PI);
  
}
main(require("fs").readFileSync("/dev/stdin", "utf8").split('\n'));