1 #include<iostream> 2 #include<cstdlib> 3 #include<cstring> 4 #include<cstdio> 5 using namespace std; 6 #define ll __int64 7 char a[1100][1100]; 8 int b[1100]; 9 int n;10 int main(){11     int i,j;12     while(cin>>n &&n){13         int t=0;14         int f=0,o=0;15         for(i=1;i<=n;i++){16             cin>>a[i];17             if(o>=2) f=1;18             if(strstr(a[i],"x")) o++;19             else o=0;20             if(strstr(a[i],"x")==NULL && i!=1 && strstr(a[i-1],"x")==NULL){21                 int k1=atoi(a[i]);22                 int k2=atoi(a[i-1]);23                 if(i%2==0){24                     if(k1<=k2) f=1;25                 }26                 else if(k1>=k2) f=1;27             }28             if(strstr(a[i],"x"))29               b[t++]=i;30         }31         if(f==1 || t==n){32             cout<<"none"<<endl;33             continue;34         }35         else if(t==0){36             cout<<"ambiguous"<<endl;37             continue;38         }39         ll min=-1e9-100,max=1e9+100;40         for(i=0;i<t;i++){41             if(b[i]%2==0){42                 if(strstr(a[b[i]-1],"x")==NULL && b[i]-1!=0){43                     int k=atoi(a[b[i]-1]);44                     if(min<k)  min=k;45                 }46                 if(strstr(a[b[i]+1],"x")==NULL && b[i]+1<=n){47                     int k=atoi(a[b[i]+1]);48                     if(min<k)  min=k;49                 }50             }51             else {52                 if(strstr(a[b[i]-1],"x")==NULL && b[i]-1!=0){53                     int k=atoi(a[b[i]-1]);54                     if(max>k) max=k;55                 }56                 if(strstr(a[b[i]+1],"x")==NULL && b[i]+1<=n){57                     int k=atoi(a[b[i]+1]);58                     if(max>k) max=k;59                 }60             }61         }62         //cout<<"max="<<max<<"min="<<min<<endl;63         if(max-min==2) cout<<min+1<<endl;64         else if(max-2>min) cout<<"ambiguous"<<endl;65         else cout<<"none"<<endl;66     }67     return 0;68 }