import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;
static import std.ascii;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] lreads(T = long)(long n){return generate(()=>readln.chomp.to!T()).take(n).array();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    long A, B, X;
    scan(A, B, X);
    real eval(real theta)
    {
        real ha = A * sin((PI / 2) - theta);
        real hb = B * sin(theta);
        // writeln(theta);
        if (ha < hb)
        {
            return A * (A * B - (A * A * sin(PI / 2 - theta)) / (2 * sin(PI - theta)));
        }
        else
        {
            return A * ((B * B * sin(theta)) / (2 * sin(PI / 2 + theta)));
        }
    }

    real ok = 0;
    real ng = 90;
    while (10.0 ^^ -15 < ng - ok)
    {
        real m = (ok + ng) / 2;
        // writeln(m, " ", eval(PI * (90 - m) / 180));
        if (X <= eval(PI * (90 - m) / 180))
        {
            ok = m;
        }
        else
        {
            ng = m;
        }
    }
    writefln("%.10f", ok);
}
