#include "testlib.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define all(a) begin(a), end(a)
#define space inf.readChar(' ')
#define endl inf.readChar('\n')
#define eof inf.readEof()
tuple<ll> read(ll min, ll max){
    ll a = inf.readLong(min, max);
    endl;
    return tuple{a};
}
template<class... T> auto read(ll min, ll max, T... t){
    ll a = inf.readLong(min, max);
    space;
    return tuple_cat(tuple{a}, read(t...));
}
string read(string p){
    return inf.readLine(p);
}
vector<ll> reads(ll N, ll min, ll max){
    auto a = inf.readLongs(N, min, max);
    endl;
    return a;
}
vector<string> read_lines(ll N, string p){
    return inf.readLines(N, p);
}
template<class... T> auto read_lines(ll N, T... t){
    vector<decltype(read(t...))> a;
    a.reserve(N);
    while(N--) a.push_back(read(t...));
    return a;
}
vector<vector<ll>> read_matrix(ll H, ll W, ll min, ll max){
    vector<vector<ll>> ans(H);
    for(auto& v : ans) v = reads(W, min, max);
    return ans;
}

const long long MIN_H = 2;
const long long MAX_H = 2000;
const long long MIN_W = 2;
const long long MAX_W = 2000;

int main() {
    registerValidation();
    
    long long H = inf.readLong(MIN_H, MAX_H);
    inf.readSpace();
    long long W = inf.readLong(MIN_W, MAX_W);
    inf.readEoln();

    for (int i = 0; i < H; i++) {
        string s = inf.readString();
        assert(s.size() == W);
        
        for (int j = 0; j < W; j++) {
            if (i == 0 && j == 0) {
                assert(s[j] == 'S');
            } else if (i == H - 1 && j == W - 1) {
                assert(s[j] == 'G');
            } else {
                assert(s[j] == '.' || s[j] == '#');
            }
        }
    }
    
    inf.readEof();
}