Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
	"reflect"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

func scanBoard() [][]int {
	ret := make([][]int, 8)
	for k := range ret {
		ret[k] = make([]int, 8)
		for l := range ret[k] {
			ret[k][l] = 0
		}
	}
	for i := 0; i < 8; i++ {
		scanner.Scan()
		row := strings.Split(scanner.Text(), "")
		if reflect.DeepEqual(row, []string{}) {
			break
		}
		for j := 0; j < 8; j++ {
			ret[i][j], _ = strconv.Atoi(row[j])
		}
	}
	return ret
}

var emptyBoard = [][]int{{0,0,0,0,0,0,0,0},
						 {0,0,0,0,0,0,0,0},
						 {0,0,0,0,0,0,0,0},
	                     {0,0,0,0,0,0,0,0},
	                     {0,0,0,0,0,0,0,0},
	                     {0,0,0,0,0,0,0,0},
	                     {0,0,0,0,0,0,0,0},
	                     {0,0,0,0,0,0,0,0}}

func main() {
	for {
		var board [][]int
		var ans string
		if board = scanBoard(); reflect.DeepEqual(board, emptyBoard) {
			break
		}
		// fmt.Println(board)
		for i := 0; i < 7; i++ {
			for j := 0; j < 7; j++ {
				if board[i][j] == 1 && board[i+1][j] == 1 && board[i][j+1] == 1 && board[i+1][j+1] == 1 {
					ans = "A"
				}
			}
		}
		for i := 0; i < 5; i++ {
			for j := 0; j < 8; j++ {
				if board[i][j] == 1 && board[i+1][j] == 1 && board[i+2][j] == 1 && board[i+3][j] == 1 {
					ans = "B"
				}
			}
		}
		for i := 0; i < 8; i++ {
			for j := 0; j < 5; j++ {
				if board[i][j] == 1 && board[i][j+1] == 1 && board[i][j+2] == 1 && board[i][j+3] == 1 {
					ans = "C"
				}
			}
		}
		for i := 0; i < 6; i++ {
			for j := 0; j < 7; j++ {
				if board[i][j+1] == 1 && board[i+1][j] == 1 && board[i+1][j+1] == 1 && board[i+2][j] == 1 {
					ans = "D"
				}
			}
		}
		for i := 0; i < 7; i++ {
			for j := 0; j < 6; j++ {
				if board[i][j] == 1 && board[i][j+1] == 1 && board[i+1][j+1] == 1 && board[i+1][j+2] == 1 {
					ans = "E"
				}
			}
		}
		for i := 0; i < 7; i++ {
			for j := 0; j < 6; j++ {
				if board[i][j+1] == 1 && board[i][j+2] == 1 && board[i+1][j] == 1 && board[i+1][j+1] == 1 {
					ans = "G"
				}
			}
		}
		for i := 0; i < 6; i++ {
			for j := 0; j < 7; j++ {
				if board[i][j] == 1 && board[i+1][j] == 1 && board[i+1][j+1] == 1 && board[i+2][j+1] == 1 {
					ans = "F"
				}
			}
		}
		fmt.Println(ans)
	}
}

C++: #include <algorithm>
#include <cmath>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <cassert>
#include <functional>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
//#define LOG(...)
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())
#define CLR(a) memset((a), 0 ,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

int main() {
	bool br = false;
	while (true){
		bool cell[8][8] = { false };
		int ans = 0;
		REP(i, 8){
			string s;
			getline(cin, s);
			if (s.empty()){
				br = true;
				break;
			}
			REP(j, 8){
				if (s[j] == '1')
					cell[i][j] = true;
			}
		}
		if (br)
			break;
		REP(i, 8){
			REP(j, 8){
				if (cell[i][j]){
					REP(k, 3)
						REP(l, 3)
						if (i + (k - 1) >= 0 && i + (k - 1) < 8 && j + (l - 1) >= 0 && j + (l - 1) < 8 && cell[i + (k - 1)][j + (l - 1)])
							ans += 1 << (8 - (k * 3 + l));
					i = 8;
					j = 8;
				}
			}
		}
		switch (ans){
		case 27:
			cout << 'A' << endl;
			break;
		case 18:
			cout << 'B' << endl;
			break;
		case 24:
			cout << 'C' << endl;
			break;
		case 22:
			cout << 'D' << endl;
			break;
		case 25:
			cout << 'E' << endl;
			break;
		case 19:
			cout << 'F' << endl;
			break;
		case 30:
			cout << 'G' << endl;
			break;
		}
	}
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<cstdio>
#include<sstream>
#include<algorithm>
#include<cmath>
#include<map>
#include<functional>
#include<queue>
#include<stack>
#include<set>
using namespace std;
int stoi(string x){stringstream ss;ss<<x;int tmp;ss>>tmp;return tmp;}
string itos(int x){stringstream ss;ss<<x;return ss.str();}
char ta[12][12];
int main(){
while(cin>>ta[0][0]){
	int y,x;
	bool f=1;
	for(int i=0;i<8;i++){
		for(int j=(i==0);j<8;j++){
			char now;
			cin>>now;
			if(now=='1'&&f){y=i,x=j;f=0;}
			ta[i][j]=now;
		}
	}
	if(ta[y][x+1]=='1'&&ta[y+1][x]=='1'&&ta[y+1][x+1]=='1')cout<<"A";
	
	else if(ta[y+1][x]=='1'&&ta[y+2][x]=='1'&&ta[y+3][x]=='1')cout<<"B";
	
	else if(ta[y][x+1]=='1'&&ta[y][x+2]=='1'&&ta[y][x+3]=='1')cout<<"C";
	
	else if(ta[y][x+1]=='1'&&ta[y+1][x+1]=='1'&&ta[y+1][x+2]=='1')cout<<"E";
	
	else if(ta[y+1][x]=='1'&&ta[y+1][x+1]=='1'&&ta[y+2][x+1]=='1')cout<<"F";
	
	else if(ta[y+2][x-1]=='1'&&ta[y+1][x]=='1'&&ta[y+1][x-1]=='1')cout<<"D";
	else cout<<"G";
	cout<<endl;
		for(int i=0;i<12;i++)for(int j=0;j<12;j++)ta[i][j]='0';
}
	
	return 0;
}

C++: #include <iostream>
using namespace std;

int main(void) {
    char c;
    int a[8][8];

    while (!cin.eof()) {
        int ci = -1, cj = -1;
        for (int i = 0; i < 8; ++i) {
            for (int j = 0; j < 8; ++j) {
                cin >> c;
                a[i][j] = int(c - '0');
                if (ci == -1 && a[i][j] == 1) {
                    ci = i;
                    cj = j;
                }
            }
        }

        if (ci <= 6 && cj <=6 && a[ci][cj] + a[ci][cj+1] + a[ci+1][cj] + a[ci+1][cj+1] == 4)
            cout << "A" << endl;
        else if (ci <= 4 && cj <=7 && a[ci][cj] + a[ci+1][cj]+a[ci+2][cj]+a[ci+3][cj] == 4)
            cout << "B" << endl;
        else if (ci <= 7 && cj <= 4 && a[ci][cj] + a[ci][cj+1] + a[ci][cj+2] + a[ci][cj+3] == 4)
            cout << "C" << endl;
        else if (ci <= 5 && 1 <= cj && a[ci][cj] + a[ci+1][cj] + a[ci+1][cj-1] + a[ci+2][cj-1] == 4)
            cout << "D" << endl;
        else if (ci <= 6 && cj <= 5 && a[ci][cj] + a[ci][cj+1] + a[ci+1][cj+1] + a[ci+1][cj+2] == 4)
            cout << "E" << endl;
        else if (ci <= 5 && cj <= 6 && a[ci][cj] + a[ci+1][cj] + a[ci+1][cj+1] + a[ci+2][cj+1] == 4)
            cout << "F" << endl;
        else if (ci <= 6 && 1 <= cj && cj <= 6 && a[ci][cj] + a[ci][cj+1] + a[ci+1][cj] + a[ci+1][cj-1] == 4)
            cout << "G" << endl;
    }
    return 0;
}