#include <bits/stdc++.h>
using namespace std;

#define IOS  ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define int  long long

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};

const int N = 1005;
int n, m, k;
char a[N][N];
int vis[N][N];
int dis[N][N];
int final[N][N];
pair<int, int> src, des;

int32_t main()
{
    IOS
    cin >> n >> m >> k;
    for(int i = 1; i <= n; i++) {
    	for(int j = 1; j <= m; j++) {
    		dis[i][j] = -1;
    	}
    }
    for(int i = 1; i <= n; i++) {
    	for(int j = 1; j <= m; j++) {
    		cin >> a[i][j];
    		if(a[i][j] == 'S') {
    			src = {i, j};
    		}
    		if(a[i][j] == 'E') {
    			des = {i, j};
    		}
    		if(a[i][j] == '#')
    			dis[i][j] = 0;
    	}
    }
    priority_queue<tuple<int, int, int>> q;
    for(int i = 1; i <= k; i++) {
    	int r, c, d;
    	cin >> r >> c >> d;
    	q.push({d, r, c});
    	vis[r][c] = 1;
    	dis[r][c] = d;
    }
    while(!q.empty()) {
    	int d, x, y;
    	tie(d, x, y) = q.top();
    	q.pop();
    	for(int i = 0; i < 4; i++) {
    		int nx = x + dx[i];
    		int ny = y + dy[i];
    		if(nx == 0 || nx > n || ny == 0 || ny > m || a[nx][ny] == '#')
    			continue;
    		if(!vis[nx][ny]) {
    			dis[nx][ny] = dis[x][y] - 1;
    			q.push({dis[nx][ny], nx, ny});
    			vis[nx][ny] = 1;
    		}
    	}
    }
    for(int i = 1; i <= n; i++) {
    	for(int j = 1; j <= m; j++) {
    		vis[i][j] = 0;
    		final[i][j] = 1e9;
    	}
    }
    if(dis[src.first][src.second] >= 0) {
    	cout << "IMPOSSIBLE" << endl;
    	exit(0);
    }
    queue<pair<int, int>> pq;
    pq.push(src);
    final[src.first][src.second] = 0;
    while(!pq.empty()) {
    	pair<int, int> tmp = pq.front();
    	int x = tmp.first;
    	int y = tmp.second;
    	pq.pop();
    	for(int i = 0; i < 4; i++) {
    		int nx = x + dx[i];
    		int ny = y + dy[i];
    		if(nx == 0 || nx > n || ny == 0 || ny > m || dis[nx][ny] >= 0)
    			continue;
    		if(!vis[nx][ny]) {
    			final[nx][ny] = final[x][y] + 1;
    			pq.push({nx, ny});
    			vis[nx][ny] = 1;
    		}
    	}
    }
    if(final[des.first][des.second] == 1e9) {
    	cout << "IMPOSSIBLE" << endl;
    } else {
    	cout << final[des.first][des.second] << endl;
    }
    return 0;
}