#include<iostream>
using namespace std;
int main()
{int spot[2][20];
 int x=0, y=1, i,n=19, times, movex=0, movey=0, correcttimes=0,key=0;
 char directions;
LOOP:
while(cin>>times)
 {if(times==0)
   {break;
   }
   for(i=19;i>-1;i--)
    {spot[x][i]=25;
     spot[y][i]=30-i;
    }
   for(i=0;i<times;i++)
    {
     cin>>directions;
       switch(directions)
        {case 'E':movex=0  ; movey=1  ;break;
         case 'W':movex=0  ; movey=-1 ;break;
         case 'N':movex=-1 ; movey=0  ;break;
         case 'S':movex=1  ; movey=0  ;break;
        }
     for(n=19;n>=1;n--)
      {spot[x][n]=spot[x][n-1];
       spot[y][n]=spot[y][n-1];
      }
       spot[x][0]+=movex;
       spot[y][0]+=movey;
    for(n=19;n>0;n--)
     {if(spot[x][0]==spot[x][n]&&spot[y][0]==spot[y][n])
       {key=2;break;
       }
     }
  
     if(key==2)
      {cout<<"The worm ran into itself on move "<<i+1<<"."<<endl;
       key=0;
       break;
      }
     if(spot[x][0]<1||spot[x][0]>50||spot[y][0]<1||spot[y][0]>50)
      {cout<<"The worm ran off the board on move "<<i+1<<"."<<endl;
       break;
     
      }
      
     if(i==times-1)
      {cout<<"The worm successfully made all "<<times<<" moves."<<endl;
       break;
      }
    
    }
 }
system("pause");
return 0;
}

测试数据：
18
NWWWWWWWWWWSESSSWS
20
SSSWWNENNNNNWWWWSSSS
30
EEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
13
SWWWWWWWWWNEE
0

但是在输完20这组数据 就会跳出，
重新输30的数据也会跳出， 
但是输18的可以到达输20的地方···
求神牛解释···