#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define REP(i,n) for(int (i)=0; (i)<(n) ;++(i)) #define REPN(i,a,n) FOR((i),(a),(a)+(n)) #define FOR(i,a,b) for(int (i)=(a); (i)<(b) ;++(i)) #define PB push_back #define MP make_pair #define SE second #define FI first #define DBG(a) cerr<<(a)< PLL; typedef vector VLL; typedef pairPI; typedef vector VI; const LL LINF=334ll<<53; const int INF=15<<26; const LL MOD=1E9+7; int main(){ cin.tie(0); ios::sync_with_stdio(false); double a,b,c,d; cin >> a >> b >> c >> d; cout << fixed << setprecision(12)<