#include <stdio.h>
#include <stdlib.h>

char s[999][999];
int book[999];
int main()
{
    int n,m,cnt=0,temp=0;
    char c;
    scanf ("%d %d %c",&n,&m,&c);
    fflush(stdin);
    int i,j;
    for (i=0;i<n;i++){
        for (j=0;j<m;j++){
            scanf ("%c",&s[i][j]);
            if (s[i][j]=='o') {
                book[cnt]=i;
                book[cnt+1]=j;
                cnt+=2;
            }
            if (s[i][j]=='x'){
                temp++;
            }
        }
        fflush(stdin);
    }
    if (!temp||!cnt){
        printf ("OK");
        exit(0);
    }
    int flag=1;//OK
    switch (c){
        case '^':
            for (cnt;cnt>1;cnt-=2){
                i=book[cnt-2];j=book[cnt-1];
                while (i>=0){
                    if (s[i][j]=='x'){
                        flag=0; goto ans;
                    }
                    i--;
                }
            }
            break;
        case 'v':
            for (cnt;cnt>1;cnt-=2){
                i=book[cnt-2];j=book[cnt-1];
                while (i<n){
                    if (s[i][j]=='x'){
                        flag=0; goto ans;
                    }
                    i++;
                }
            }
            break;
        case '<':
            for (cnt;cnt>1;cnt-=2){
                i=book[cnt-2];j=book[cnt-1];
                while (j>=0){
                    if (s[i][j]=='x'){
                        flag=0; goto ans;
                    }
                    j--;
                }
            }
            break;
        case '>':
            for (cnt;cnt>1;cnt-=2){
                i=book[cnt-2];j=book[cnt-1];
                while (j<m){
                    if (s[i][j]=='x'){
                        flag=0; goto ans;
                    }
                    j++;
                }
            }
            break;
    }

    ans:
    if (flag) printf ("OK");
    else printf("GG");

    system("pause");
    
    return 0;
}