my voids don't give any input, but still it says crashed

This is my code:
#include<iostream>
#include<string>
using namespace std;
long int n,len;
string a;
string ch;
long int pp,xx,ii,st,x;
bool st_match()
{
     pp=ch.length();
     if(xx+pp>len)
     return false;
     for(ii=xx;ii<xx+pp;ii++)
     if(a[ii]!=ch[ii-xx])
     return false;
     return true;
}

    bool p;
void DFS()
{
     if(p)
     return ;
     if(x==len)
     {
               p=true;
               cout<<"YES"<<endl;
               return ;
     }
     st=xx;
     xx=x;
     ch="one";
          if(st_match()){x+=3;DFS();x-=3;}
          ch="puton";
              if(st_match()){x+=5;DFS();x-=5;}
              ch="input";
                  if(st_match()){x+=5;DFS();x-=5;}
                  ch="in";
                      if(st_match()){x+=2;DFS();x-=2;}
                      ch="output";
                          if(st_match()){x+=6; DFS(); x-=6;}
                          ch="out";
                              if(st_match()){x+=3; DFS(); x-=3;}
                              xx=st;
                              return  ;

}
int main(){
    cin>>n;
    for(int i=0;i<n;i++)
    {
       cin>>a;
       p=false;
       len=a.length();
       x=0;
       DFS();
           if(!p)
           cout<<"NO"<<endl;
    }
    cin>>n;
return 0;
}

Edited by author 16.11.2010 18:32