hdu 1022自己试了好多数据，极端数据也试了，可是就是WA，求指教

#include
#include

using namespace std;

int main()
{
int i,j,k,n,l;
int s[20]={0};
char str1[10];char str2[10];
stack train_station;
while(cin>>n>>str1>>str2)
{
for(k=0;k<20;k++)
{
s[k]=0;
}
i=0;j=0;k=0;l=2*n;
while(l)
{
if(k==0)
{
train_station.push(str1[i++]);
s[k++]=1;
}
else
{
if(!(train_station.empty())&&train_station.top()==str2[j])
{
train_station.pop();
j++;
s[k++]=2;
}
else
{
if(i!=n)
{train_station.push(str1[i++]);
s[k++]=1;}
}
}
l--;
}
if(i==n&&j==n)
{
cout<<"Yes."<<endl;
for(int a=0;a<20;a++)
{
if(s[a]==1)
{cout<<"in"<<endl;}
if(s[a]==2)
{cout<<"out"<<endl;}
}
cout<<"FINISH"<<endl;
}
if(i==n&&j<n)
{
cout<<"No."<<endl;
cout<<"FINISH"<<endl;
}
}
return 0;
}