#include<iostream>#include<cstdio>#include<string>#include<stack>#include<cstring>#include<cstdlib>#include<cctype>using namespace std;int main(){ string str; while(getline(cin,str)) { if(str=="()") break; stack<double> q; for(int i=0;i<str.size();) { if(str[i]==' '||str[i]=='(') i++; else if(isdigit(str[i])||str[i]=='-') //考虑负数 { string temp; for(;i<str.size()&&str[i]!=' '&&str[i]!=')';i++) { temp+=str[i]; } double x=atof(temp.c_str()); q.push(x); } else { double p,x,y; y=q.top();q.pop(); x=q.top();q.pop(); p=q.top();q.pop(); double cnt=p*(x+y)+(1-p)*(x-y); q.push(cnt); i++; } } double ans=q.top(); printf("%.2lfn",ans); } return 0;}
