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 <iostream>
#include <cstdio>
using namespace std;

int main() {
 NEXT:
  char x;
  int k=0;
  while(1) {
    cin.get(x);
    if(x == '1') {
      k = k % 7;
      break;
    }
    k++;
  }
  cin.get(x);
  if(x == '1') {// A,C,E,G
    cin.get(x);
    if(x == '1') // C
      cout << "C" << endl;
    else if(x == '0') {//A,E,G
      for(int i=0;i<6;i++){
        cin.get(x);
      }
      if(x == '1')
        cout << "G" << endl; // G
      else if(x == '0') {
        cin.get(x);
        if(x == '1')
          cout << "A" << endl; // A
        else
          cout << "E" << endl; // E
      }
    }
  }
  else if(x == '0') {//B,D,F
    for(int i=0;i<6;i++) {
      cin.get(x);
    }
    if(x == '1')
      cout << "D" << endl;
    else if(x == '0') {
      cin.get(x);
      cin.get(x);
      if(x == '1')
        cout << "F" << endl;
      else
        cout << "B" << endl;
    }
  }
  while(1) {
    cin.get(x);
    if(x == '\n') {
      cin.get(x);
      if(x == '\n')
        goto NEXT;
    }
  }
}

C++: #include <iostream>
int main(){
	while(1){
		std::string s[8];

		int x = 0,y = 0;
		for(int i=0;i<8;i++){
			std::cin >> s[i];
			if(std::cin.eof())return 0;
		}
		
		for(int i=0;i<64;i++)
			if(s[i/8][i%8] == '1'){x=i%8,y=i/8;break;}

		char res;
		if(y+1 < 8 && s[y+1][x] == '1'){
			if(x-1 >= 0 && s[y+1][x-1] == '1'){
				if(x+1 < 8 && s[y][x+1] == '1'){
					res = 'G';
				}
				else{
					res = 'D';
				}
			}
			else if(x+1 < 8 && s[y+1][x+1] == '1'){
				if(s[y][x+1] == '1'){
					res = 'A';
				}
				else{
					res = 'F';
				}
			}
			else{
				res = 'B';
			}
		}
		else{
			if(x+1 < 8 && y+1 < 8 && s[y+1][x+1] == '1'){
				res = 'E';
			}
			else{
			res = 'C';
			}
		}

		std::cout << res << std::endl;
	}
}

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

#define REP(i, s, n) for (int i = s; i < n; ++i)
#define rep(i, n) REP(i, 0, n)
#define SORT(c) sort((c).begin(), (c).end())
#define IINF INT_MAX
#define LLINF LLONG_MAX
#define DEBUG false

int main()
{
    while (true)
    {
        string a[8];
        vector<int> tracex;
        vector<int> tracey;
        bool flag = false;
        rep(i, 8) if(!(cin >> a[i])) return 0;
        rep(i, 8)
            rep(j, 8) if (a[i][j] == '1')
        {
            tracex.push_back(j);
            tracey.push_back(i);
        }
        REP(i, 1, tracex.size())
        tracex[i] -= tracex[0];
        REP(i, 1, tracey.size())
        tracey[i] -= tracey[0];
        //tracex[0]=0;tracey[0]=0;
        if (tracex[3] == 1 && tracey[3] == 1)
            cout << "A" << endl;
        if (tracex[3] == 3)
            cout << "C" << endl;
        if (tracey[3] == 3)
            cout << "B" << endl;
        if (tracex[1] == -1 && tracey[3] == 2)
            cout << "D" << endl;
        if (tracex[3] == 2)
            cout << "E" << endl;
        if (tracex[1] == 1 && tracey[3] == 2)
            cout << "F" << endl;
        if (tracex[2] == -1 && tracey[2] == 1)
            cout << "G" << endl;
        if (flag)
            break;
    }
    return 0;
}

C++:  
 #include<iostream>
 #include<stdio.h>
 #include<string>
 #include<math.h>
 #include<iomanip>
 #include<algorithm>
 #include<string.h>
 #include<cctype>
 #include<map>
 #include<set>
 #include<vector>
 #include<sstream>
 #include<stack>
 #include<queue>
 
 using namespace std;

 char arr[8][8];
 
 int main()
 {
   while(cin>>arr[0][0])
   {
     int x[4],y[4];
     int cnt1,cnt2;
     cnt1=cnt2=0;
     if(arr[0][0]=='1') 
     {
       x[cnt1++]=0;
       y[cnt2++]=0;                   
     }
     for(int i=0;i<8;i++)
     {
       for(int j=0;j<8;j++)
       {
           if(i==0&&j==0) continue;
           else
           {
             cin>>arr[i][j];
             if(arr[i][j]=='1')
             {
               x[cnt1++]=j;
               y[cnt2++]=i;                
             }
           }    
                 
       }        
     }             
     if(x[0]==x[1]&&x[2]==x[3]&&y[1]==y[0]+1&&y[3]==y[2]+1) cout<<"A"<<endl;
     else if(y[0]==y[1]&&y[1]==y[2]&&y[2]==y[3]) cout<<"B"<<endl;
     else if(x[0]==x[1]&&x[1]==x[2]&&x[2]==x[3]) cout<<"C"<<endl;
     else if(x[1]==x[2]&&y[0]==y[3]+1) cout<<"D"<<endl;
     else if(y[1]==y[2]&&(y[3]==y[0]+2)) cout<<"E"<<endl;
     else if(x[1]==x[2]&&x[3]==x[0]+1) cout<<"F"<<endl;
     else cout<<"G"<<endl;        
   }
   //while(1);
   return 0;
 }