#include<bits/stdc++.h>
using namespace std;
int main() {
	int n,m,oko=1,okx=1,x,y;
	char ht[102][102],zlfx;
	cin>>n>>m>>zlfx;
	for(int i=0;i<n;i++)
		for(int j=0;j<m;j++)
		{
			cin>>ht[i][j];
			if(ht[i][j]=='o'){oko=0;x=i;y=j;}
			if(ht[i][j]=='x')okx=0;
		}
	if(oko||okx){cout<<"OK";return 0;}
	switch (zlfx) {
		case '^':
			for(;x>=0;x--)if(ht[x][y]=='x'){cout<<"GG";return 0;}
			break;
		case 'v':
			for(;x<n;x++)if(ht[x][y]=='x'){cout<<"GG";return 0;}
			break;
		case '<':
			for(;y>=0;y--)if(ht[x][y]=='x'){cout<<"GG";return 0;}
			break;
		default:
			for(;y<m;y++)if(ht[x][y]=='x'){cout<<"GG";return 0;}
			break;
	}
	cout<<"OK";
	return 0;
}