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++: #include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;

#define loop(i,a,b) for(int i=(a); i<(int)(b); i++)
#define rep(i,b) loop(i,0,b)
#define all(c) (c).begin(), (c).end()
 
typedef vector<int> vi;
typedef vector<vi> vvi;

int main() {
  bool field[12][12] = {};
  string s;
  while(cin >> s) {
    rep(i, 8) {
      field[0][i] = s[i] == '1';
    }
    loop(i, 1, 8) {
      cin >> s;
      loop(j, 0, 8) {
        field[i][j] = s[j] == '1';
      }
    }
   
    char ans = '.';
    rep(i, 8) {
      rep(j, 8) {
        if(field[i][j]) {
          if(field[i][j+1] && field[i+1][j] && field[i+1][j+1]) ans = 'A';
          else if(field[i+1][j] && field[i+2][j] && field[i+3][j]) ans = 'B';
          else if(field[i][j+1] && field[i][j+2] && field[i][j+3]) ans = 'C';
          else if(field[i][j+1] && field[i+1][j+1] && field[i+1][j+2]) ans = 'E';
          else if(field[i+1][j] && field[i+1][j+1] && field[i+2][j+1]) ans = 'F';
          else if(field[i+1][j] && field[i+1][j-1] && field[i+2][j-1]) ans = 'D';
          else ans = 'G';
          break;
        }
      }
      if(ans != '.') break;
    }
    cout << ans << endl;
    getline(cin, s);
  }
}

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

#define all(c) (c).begin(), (c).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define pb(e) push_back(e)
#define mp(a, b) make_pair(a, b)
#define fr first
#define sc second

const int INF=100000000;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
using namespace std;
typedef pair<int ,int > P;
typedef long long ll;

string grid[8];
bool is_A(int i,int j) {
    if(i+1>=8 || j+1>=8) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i+1][j]=='0') return false;
    if(grid[i][j+1]=='0') return false;
    if(grid[i+1][j+1]=='0') return false;
    return true;

}
bool is_B(int i,int j) {
    if(i+3>=8) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i+1][j]=='0') return false;
    if(grid[i+2][j]=='0') return false;
    if(grid[i+3][j]=='0') return false;
    return true;
}
bool is_C(int i,int j) {
    if(j+3>=8) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i][j+1]=='0') return false;
    if(grid[i][j+2]=='0') return false;
    if(grid[i][j+3]=='0') return false;
    return true;
}
bool is_D(int i,int j) {
    if(i+2>=8||j-1<0) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i+1][j]=='0') return false;
    if(grid[i+1][j-1]=='0') return false;
    if(grid[i+2][j-1]=='0') return false;
    return true;
}
bool is_E(int i,int j) {
    if(i+1>=8||j+2>=8) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i][j+1]=='0') return false;
    if(grid[i+1][j+1]=='0') return false;
    if(grid[i+1][j+2]=='0') return false;
    return true;
}
bool is_F(int i,int j) {
    if(j+1>=8||i+2>=8) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i+1][j]=='0') return false;
    if(grid[i+1][j+1]=='0') return false;
    if(grid[i+2][j+1]=='0') return false;
    return true;
}
bool is_G(int i,int j) {
    if(i+1>=8||j-2<0) return false;
    if(grid[i][j]=='0') return false;
    if(grid[i][j-1]=='0') return false;
    if(grid[i+1][j-1]=='0') return false;
    if(grid[i+1][j-2]=='0') return false;
    return true;
}
void solve() {
    rep(i,8) rep(j,8) {

        if(is_A(i,j)) {
            cout<<"A"<<endl;
            return;
        }
        if(is_B(i,j)) {
            cout<<"B"<<endl;
            return;
        }
        if(is_C(i,j)) {
            cout<<"C"<<endl;
            return;
        }
        if(is_D(i,j)) {
            cout<<"D"<<endl;
            return;
        }
        if(is_E(i,j)) {
            cout<<"E"<<endl;
            return;
        }
        if(is_F(i,j)) {
            cout<<"F"<<endl;
            return;
        }
        if(is_G(i,j)) {
            cout<<"G"<<endl;
            return;
        }
        if(is_B(i,j)) {
            cout<<"B"<<endl;
            return;
        }
        if(is_B(i,j)) {
            cout<<"B"<<endl;
            return;
        }
    }

    cout<<"hoge"<<endl;
}
int main() {
    while(cin>>grid[0]) {
        rep(i,7) cin>>grid[i+1];
        solve();

    }
    return 0;
}