Codeforces 8B

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<string>
#define DEBUG(...) fprintf(stderr,__VA_ARGS__)
using namespace std;
const int MAXL=502;
string s;
bool vis[MAXL][MAXL];
int main()
{
#ifndef ONLINE_JUDGE
    freopen("8B.in","r",stdin);
    freopen("8B.out","w",stdout);
#endif
    cin>>s;
    int x=250,y=250;
    vis[x][y]=1;
    for(int i=0;i<s.size();i++)
    {
        char c=s[i];
        if(c=='L')
            x-=1;
        else if(c=='R')
            x+=1;
        else if(c=='U')
            y+=1;
        else y-=1;
        DEBUG("%d %d
",x,y);
        if(vis[x][y]==1)
        {
            printf("BUG
");
            return 0;
        }
        else if(c=='R'&&(vis[x+1][y]==1||vis[x][y+1]==1||vis[x][y-1]==1))
        {
            printf("BUG
");
            return 0;
        }
        else if(c=='L'&&(vis[x-1][y]==1||vis[x][y+1]==1||vis[x][y-1]==1))
        {
            printf("BUG
");
            return 0;
        }
        else if(c=='D'&&(vis[x-1][y]==1||vis[x+1][y]==1||vis[x][y-1]==1))
        {
            printf("BUG
");
            return 0;
        }
        else if(c=='U'&&(vis[x-1][y]==1||vis[x][y+1]==1||vis[x+1][y]==1))
        {
            printf("BUG
");
            return 0;
        }
        vis[x][y]=1;
    }
    printf("OK
");
}