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(), "")
		for j := 0; j < 8; j++ {
			ret[i][j], _ = strconv.Atoi(row[j])
		}
	}
	return ret
}

func main() {
	for {
		var board [][]int
		var ans string
		if board = scanBoard(); reflect.DeepEqual(board, [][]int{}) {
			break
		}
		fmt.Println(board)
		for i := 0; i < 8; i++ {
			for j := 0; j < 8; 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 < 8; 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 < 8; 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 < 8; i++ {
			for j := 0; j < 8; 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 < 8; i++ {
			for j := 0; j < 8; 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 < 8; i++ {
			for j := 0; j < 8; 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 < 8; i++ {
			for j := 0; j < 8; 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 <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <cassert>

using namespace std;


#define all(c) ((c).begin()), ((c).end())
#define debug(c) cerr << "> " << #c << " = " << (c) << endl;
#define iter(c) __typeof((c).begin())
#define present(c, e) ((c).find((e)) != (c).end())
#define cpresent(c, e) (find(all(c), (e)) != (c).end())
#define tr(i, c) for (iter(c) i = (c).begin(); i != (c).end(); i++)
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, a, b) for (int i = (int)(a); i <= (int)(b); i++)

#define mp make_pair
#define fst first
#define snd second
#define pb push_back


const double EPS = 1e-10;


typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef complex<double> P;

#define VECTOR(a) VECTOR_((a), sizeof(a) / sizeof(a[0]))

template <typename T>
std::vector<T> VECTOR_(T *array, std::size_t size) {
  return std::vector<T>(array, array + size);
}

int main(){
	int m[] = {33,1111,15,132,63,231,36};
	for(int a[8]; cin >> a[0]; ) {
		rep(i, 7) cin >> a[i + 1];
		rep(i, 8) {
			int b = 0;
			rep(j, 10) {
				if(a[i] % 10) b += (1 << j);
				a[i] /= 10;
			}
			a[i] = b;
		}
		for(; ; ) {
			bool flg = false;
			rep(j, 8) flg |= a[j] & 1;
			if(!flg) rep(j, 8) a[j] >>= 1;
			else break;
		}
		int k = 0;
		rep(i, 8) if(a[i] != 0) {
			k = k * 10 + a[i];
		}
		rep(i, 7) if(m[i] == k) cout << (char)('A' + i) << endl;
	}
	
	return 0;
}

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

int main() {
  char str[20][20];
  while(1) {
    for ( int i = 4; i < 12; i++ ){
      for ( int j = 4; j < 12; j++ ) {
      cin >> str[i][j];
      if ( cin.eof() ) return 0;
      }
    }
    char ans;
    for ( int i = 0; i < 8; i++ ) {
      for ( int j = 0; j < 8; j++ ) {
      if ( str[i][j] == '1' && str[i][j+1] == '1' && 
	   str[i+1][j] == '1' && str[i+1][j+1] == '1' ) ans = 'A';
      else if ( str[i][j] == '1' && str[i+1][j] == '1' &&
		str[i+2][j] == '1' && str[i+3][j] =='1' ) ans = 'B';
      else if ( str[i][j] == '1' && str[i][j+1] == '1' &&
		str[i][j+2] == '1' && str[i][j+3] == '1' ) ans = 'C';
      else if ( str[i][j] == '1' && str[i+1][j-1] == '1' &&
		str[i+1][j] == '1' && str[i+2][j-1] == '1' ) ans = 'D';
      else if ( str[i][j] == '1' && str[i][j+1] == '1' &&
		str[i+1][j+1] == '1' && str[i+1][j+2] == '1' ) ans = 'E';
      else if ( str[i][j] == '1' && str[i+1][j] == '1' &&
		str[i+1][j+1] == '1' && str[i+2][j+1] == '1' ) ans = 'F';
      else if ( str[i][j] == '1' && str[i][j+1] == '1' &&
		str[i+1][j-1] == '1' && str[i+1][j] == '1' ) ans = 'G';
							 
      }
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <string>
#include <map>
#include <algorithm>
#include <cmath>
#include <numeric>
#include <stack>
using namespace std;

#define REP(i,n) for(int (i)=0; (i)<(n); (i)++)
#define For(i,a,b) for(int (i)=(a); (i)<(b); (i)++)
#define PUSH(n,v) for(int i=0; i<(n); i++) {int j; cin >> j; v.push_back(j);}

bool hasA(int bd[8][8]) {
    for (int i = 0; i < 7; i++) {
        for (int j = 0; j < 7; j++) {
            if (bd[i][j] && bd[i][j+1] && bd[i+1][j] && bd[i+1][j+1]) return true;
        }
    }
    return false;
}

bool hasB(int bd[8][8]) {
    for (int i = 0; i < 5; i++) {
        for (int j = 0; j < 8; j++) {
            if (bd[i][j] && bd[i+1][j] && bd[i+2][j] && bd[i+3][j]) return true;
        }
    }
    return false;
}

bool hasC(int bd[8][8]) {
    for (int i = 0; i < 8; i++) {
        for (int j = 0; j < 5; j++) {
            if (bd[i][j] && bd[i][j+1] && bd[i][j+2] && bd[i][j+3]) return true;
        }
    }
    return false;
}

bool hasD(int bd[8][8]) {
    for (int i = 0; i < 6; i++) {
        for (int j = 0; j < 7; j++) {
            if (bd[i][j+1] && bd[i+1][j] && bd[i+1][j+1] && bd[i+2][j]) return true;
        }
    }
    return false;
}

bool hasE(int bd[8][8]) {
    for (int i = 0; i < 7; i++) {
        for (int j = 0; j < 6; j++) {
            if (bd[i][j] && bd[i][j+1] && bd[i+1][j+1] && bd[i+1][j+2]) return true;
        }
    }
    return false;
}

bool hasF(int bd[8][8]) {
    for (int i = 0; i < 6; i++) {
        for (int j = 0; j < 7; j++) {
            if (bd[i][j] && bd[i+1][j] && bd[i+1][j+1] && bd[i+2][j+1]) return true;
        }
    }
    return false;
}

bool hasG(int bd[8][8]) {
    for (int i = 0; i < 7; i++) {
        for (int j = 0; j < 6; j++) {
            if (bd[i][j+1] && bd[i][j+2] && bd[i+1][j] && bd[i+1][j+1]) return true;
        }
    }
    return false;
}

int main36() {
    string s;
    int bd[8][8];
    while(cin >> s) {
        REP(i,8) bd[0][i] = s[i] - '0';
        REP(j,7) {
            cin >> s;
            REP(i,8) bd[j+1][i] = s[i] - '0';
        }
        // input ends
        if (hasA(bd)) cout << "A" << endl;
        else if (hasB(bd)) cout << "B" << endl;
        else if (hasC(bd)) cout << "C" << endl;
        else if (hasD(bd)) cout << "D" << endl;
        else if (hasE(bd)) cout << "E" << endl;
        else if (hasF(bd)) cout << "F" << endl;
        else if (hasG(bd)) cout << "G" << endl;
    }
    return 0;
}