#include<iostream>#include<algorithm>#include<cstdio>#include<stack>#include<string.h>#include<map>using namespace std;map<char,long long >M;map<char,int>ma;string tem;char root[2000];int Judge(char a){ if(a>='A') return 1; return 0;}void Convect(char ch[]){ stack<char> start; int len=strlen(ch); int i; int Top=0; for(i=0; i<len; i++) { if(Judge(ch[i])) { root[Top++]=ch[i]; } else { switch(ch[i]) { case '+': case '-': case '/': case '*': while((!start.empty())&&ma[start.top()]>=ma[ch[i]]) { root[Top++]=start.top(); start.pop(); } start.push(ch[i]); break; } } } while(!start.empty()) { root[Top++]=start.top(); start.pop(); } root[Top]=0;}long long sum(){ stack<long long> end; int len=strlen(root); int i; for(i=0; i<len; i++) { if(Judge(root[i])) { end.push(M[root[i]]); } else { long long num1,num2; num1=end.top(); end.pop(); num2=end.top(); end.pop(); switch(root[i]) { case '/': end.push(num2/num1); break; case '*': end.push(num1*num2); break; case '+': end.push(num1+num2); break; case '-': end.push(-num1+num2); break; } } } return end.top();}int main(){ long long ans; char a[2000]; ma['*']=2; ma['/']=2; ma['+']=1; ma['-']=1; while(cin>>tem) { M.clear(); int flag=0; memset(root,0,sizeof(root)); for(int i=0; i<tem.size()-1; i++) { if(tem[i]=='/'&&tem[i+1]=='0') { printf("impossible\n"); flag=1; break; } } if(flag) continue; int Len=0; char step='A'; ans=0; for(int i=0; i<tem.size(); i++) { if(tem[i]<'0'||tem[i]>'9') { M[step]=ans/10; a[Len++]=step; step++; a[Len++]=tem[i]; ans=0; continue; } ans=(ans+tem[i]-'0')*10; } M[step]=ans/10; a[Len++]=step; step++; a[Len++]='\0'; Convect(a); ans=sum(); printf("%lld\n",ans); } return 0;}
