import std.stdio, std.string, std.conv, std.math;

void main() {
    double[] tmp = readln.split.to!(double[]);
    double a = tmp[0], b = tmp[1], x = tmp[2];
    double c = 2.0 * x / (a * a) - b;
    if (c > 0) {
        writefln("%.10f", 90.0 - atan(a / (b - c)) * 180.0 / PI);
    } else {
        double d = 2.0 * x / (a * b);
        writefln("%.10f", 90.0 - atan(d / b) * 180.0 / PI);
    }
}