Language: C++

#include<iostream>
#include<string>
#include<cstdlib>

using namespace std;

int stoi(string s){
  return atoi(s.c_str());
}

int main(){
  for(int N;cin>>N,N;){
    string s[1234];
    for(int i=0;i<N;i++){
      cin>>s[i];
    }
    bool f=false;
    int lt=1e9+9,ht=-1e9+9;
    for(int i=0;i<N-1;i++){
      if(s[i][0]=='x'){
	if(s[i+1][0]=='x'){
	  f=true;
	}else{
	  if(i%2==0){
	    lt=min(lt,stoi(s[i+1]));
	  }else{
	    ht=max(ht,stoi(s[i+1]));
	  }
	}
      }else{
	if(s[i+1][0]=='x'){
	  if((i+1)%2==0){
	    lt=min(lt,stoi(s[i]));
	  }else{
	    ht=max(ht,stoi(s[i]));
	  }
	}else{	      
	  if(i%2){
	    f|=stoi(s[i])<=stoi(s[i+1]);
	  }else{
	    f|=stoi(s[i])>=stoi(s[i+1]);
	  }
	}
      }
    }
    if(f||lt-ht<2){
      cout<<"none"<<endl;
    }else if(lt-ht>2){
      cout<<"ambiguous"<<endl;
    }else{
      cout<<lt-1<<endl;
    }
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:25:27: error: call of overloaded 'stoi(std::string&)' is ambiguous
   25 |             lt=min(lt,stoi(s[i+1]));
      |                       ~~~~^~~~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
In file included from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:27:27: error: call of overloaded 'stoi(std::string&)' is ambiguous
   27 |             ht=max(ht,stoi(s[i+1]));
      |                       ~~~~^~~~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:33:27: error: call of overloaded 'stoi(std::string&)' is ambiguous
   33 |             lt=min(lt,stoi(s[i]));
      |                       ~~~~^~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:35:27: error: call of overloaded 'stoi(std::string&)' is ambiguous
   35 |             ht=max(ht,stoi(s[i]));
      |                       ~~~~^~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:39:20: error: call of overloaded 'stoi(std::string&)' is ambiguous
   39 |             f|=stoi(s[i])<=stoi(s[i+1]);
      |                ~~~~^~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:39:32: error: call of overloaded 'stoi(std::string&)' is ambiguous
   39 |             f|=stoi(s[i])<=stoi(s[i+1]);
      |                            ~~~~^~~~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:41:20: error: call of overloaded 'stoi(std::string&)' is ambiguous
   41 |             f|=stoi(s[i])>=stoi(s[i+1]);
      |                ~~~~^~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
a.cc:41:32: error: call of overloaded 'stoi(std::string&)' is ambiguous
   41 |             f|=stoi(s[i])>=stoi(s[i+1]);
      |                            ~~~~^~~~~~~~
a.cc:7:5: note: candidate: 'int stoi(std::string)'
    7 | int stoi(string s){
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~