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)
		fmt.Scanln()
	}
}

C++: 
#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iostream>
#include <memory>
#include <string>

#include <algorithm>
#include <complex>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <vector>

using namespace std;

#ifdef _MSC_VER
#define __typeof__ decltype
#endif

#define ITER(c)         __typeof__((c).begin())
#define FOREACH(it, c)  for (ITER(c) it=(c).begin(); it != (c).end(); ++it)
#define RITER(c)        __typeof__((c).rbegin())
#define RFOREACH(it, c) for (RITER(c) it=(c).rbegin(); it != (c).rend(); ++it)
#define REP(i, n)       REPEAT(i, 0, n)
#define REPEAT(i, k, n) for (int i = (k); i < (n); ++i)
#define REVREP(i, n)    for (int i = ((n)-1); i >= 0; --i)
#define FIND(c, n)      std::find((c).begin(), (c).end(), (n));
#define BSEARCH(c, n)   std::binary_search((c).begin(), (c).end(), (n))
#define LLPOW(p1,p2)    ((ll)pow((double)(p1), (int)p2))
#define ESIZEOF(A)      (sizeof(A)/sizeof((A)[0]))
#define MIN(p1,p2)      (((p1)<(p2))?(p1):(p2))
#define MAX(p1,p2)      (((p1)>(p2))?(p1):(p2))
#define CIN_NO_SYNC     do { cin.tie(0); ios_base::sync_with_stdio(false); } while(0)
#define GETSTR(p)       fgets((p), sizeof(p), stdin)
#define CHOMP(p)        do{ char *_q = (p) + strlen(p)-1; if(*_q == '\n') *_q = 0; } while(0)

typedef long long ll;
typedef unsigned long long ull;

#define X real()
#define Y imag()
typedef double D;
typedef complex<D> P;
#define EPS (1e-9)

inline D inprd(const P &a, const P &b){ return (conj(a) * b).X; }
inline D outprd(const P &a, const P &b){ return (conj(a) * b).Y; }
inline D sign(D d){ return (d<0)?-1:d>0?1:0; }

#ifdef _DEBUG
#define pf printf
#define pr(n) do { cout << #n " = " << (n) << endl; } while(0)
#else
#define pf(...) /* */
#define pr(...) /* */
#endif

int table[7][6] = {
    { 1,0, 0,1, 1,1 },  // A
    { 0,1, 0,2, 0,3 },  // B
    { 1,0, 2,0, 3,0 },  // C
    {-1,1, 0,1,-1,2 },  // D
    { 1,0, 1,1, 2,1 },  // E
    { 0,1, 1,1, 1,2 },  // F
    { 1,0,-1,1, 0,1 },  // G
};

int main(){
    deque<string> sv;
    string s;
    cin.binary;
    while(getline(cin, s)){
        if(s == "") continue;
        sv.push_back(s);
        s = "";
    }

    if(sv.size() % 8 != 0) throw;
    int n = sv.size() / 8;
    REP(i,n){
        char m[8][8];
        REP(y,8){
            string s = sv.front(); sv.pop_front();
            REP(x,8){
                m[y][x] = s[x] - '0';
            }
        }
        bool f = false;
        REP(y,8) REP(x,8){
            if(m[y][x]){
                REP(t,7){
                    bool f2 = true;
                    REP(u,3){
                        int nx = x + table[t][u*2+0];
                        int ny = y + table[t][u*2+1];
                        if(nx < 0 || nx >= 8 || ny < 0 || ny >= 8 || m[ny][nx] == 0){
                            f2 = false; break;
                        }
                    }
                    if(f2){
                        printf("%c\n", 'A' + t);
                        goto END;
                    }
                }
            }
        }
END:;
    }

    return 0;
}

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

vector <string> f;

const string P[7][4] = {
	{// A
		"1100",
		"1100",
		"0000",
		"0000"
	},
	{// B
		"1000",
		"1000",
		"1000",
		"1000"
	},
	{// C
		"1111",
		"0000",
		"0000",
		"0000"
	},
	{// D
		"0100",
		"1100",
		"1000",
		"0000"
	},
	{// E
		"1100",
		"0110",
		"0000",
		"0000"
	},
	{// F
		"1000",
		"1100",
		"0100",
		"0000"
	},
	{// G
		"0110",
		"1100",
		"0000",
		"0000"
	},
};

bool check( int x, int y, int k )
{
	for ( int i = 0; i < 4; i++ )
	{
		for ( int j = 0; j < 4; j++ )
		{
			int nx = x + j;
			int ny = y + i;
			if ( P[k][i][j] == '1' )
			{
				if ( nx < 0 || nx > 8 || ny < 0 || ny > 8 )
				{
					return false;
				}
				if ( P[k][i][j] != f[ny][nx] )
					return false;
			}
		}
	}
	return true;
}

int main( void )
{
	while ( cin.eof() == false )
	{
		f = vector <string>(8);
		string line;
		for ( int i = 0; i < 8; i++ )
		{
			getline( cin, line );
			f[i] = line;
			if ( cin.eof() ) break;
		}
		if ( cin.eof() ) break;
		getline( cin, line );

		char answer = 'A';
		bool not_found = true;
		for ( int i = 0; not_found && i < 8; i++ )
		{
			for ( int j = 0; not_found && j < 8; j++ )
			{
				for ( int k = 0; not_found && k < 7; k++ )
				{
					if ( check( j, i, k ) )
					{
						answer += k;
						not_found = false;
					}
				}
			}
		}

		cout << answer << endl;
	}
	return 0;
}