#include <iostream> #include <algorithm> #include <functional> #include <string> #include <climits> #include <vector> #include <numeric> #include <complex> #include <map> #include <bitset> using namespace std; //#define __int64 long long #define long __int64 #define REP(i,a,b) for(int i=a;i<b;i++) #define rep(i,n) REP(i,0,n) const int Vecy[4] = {0,-1,0,1}; const int Vecx[4] = {1,0,-1,0}; int main(){ int a,b,c,d; double ans; cin >> a >> b >> c >> d; if(a * d == b * c){ ans = c + d; }else if(a * d > b * c){ ans = c + (double(c) * b / a); }else{ ans = d + (double(d) * a / b); } cout.precision(13); cout << fixed << ans << endl; return 0; }