// dfmt off
T lread(T=long)(){return readln.chomp.to!T;}T[] lreads(T=long)(long n){return iota(n).map!((_)=>lread!T).array;}
T[] aryread(T=long)(){return readln.split.to!(T[]);}void arywrite(T)(T a){a.map!text.join(' ').writeln;}
void scan(L...)(ref L A){auto l=readln.split;foreach(i,T;L){A[i]=l[i].to!T;}}alias sread=()=>readln.chomp();
void dprint(L...)(lazy L A){debug{auto l=new string[](L.length);static foreach(i,a;A)l[i]=a.text;arywrite(l);}}
static immutable MOD=10^^9+7;alias PQueue(T,alias l="b<a")=BinaryHeap!(Array!T,l);import std;
// dfmt on

void main()
{
    long A, B, H, M;
    scan(A, B, H, M);
    real h = 2 * PI * ((H * 60 + M) / (12.0 * 60));
    real m = 2 * PI * (M / 60.0);
    real hx = A * cos(h);
    real hy = A * sin(h);
    real mx = B * cos(m);
    real my = B * sin(m);
    writefln("%.10f", sqrt((hx - mx) ^^ 2 + (hy - my) ^^ 2));
}
