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 <vector>
#include <iostream>
#include <utility>
#include <algorithm>
#include <string>
#include <deque>
#include <queue>
#include <tuple>
#include <queue>
#include <functional>
#include <cmath>
#include <iomanip>
#include <map>
#include <set>
#include <numeric>
#include <unordered_map>
#include <unordered_set>
#include <complex>
#include <iterator>
#include <array>
#include <memory>
#include <stack>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define loop(i,s,n) for(int i=s;i<n;i++)
#define all(in) in.begin(), in.end()
template<class T, class S> void cmin(T &a, const S &b) { if (a > b)a = b; }
template<class T, class S> void cmax(T &a, const S &b) { if (a < b)a = b; }
#define MAX 9999999
using namespace std;
typedef pair<int, int> pii;
typedef pair<double,double>pdd;
typedef pair<ll,ll>pll;
int main(){
    char tiya[8][8];
    while(cin>>tiya[0][0]){
    vector<pii>gotiusa;
    rep(i,8)rep(j,8){
        if(i==0&&j==0)continue;
        cin>>tiya[i][j];
        if(tiya[i][j]=='1')gotiusa.push_back(pii(i,j));
    }
    int tate=0;
    int yoko=0;
    pii t=pii(-INF,INF),y=pii(-INF,INF);
    rep(i,gotiusa.size()){
        cmax(t.first,gotiusa[i].first);
        cmin(t.second,gotiusa[i].first);
        cmax(y.first,gotiusa[i].second);
        cmin(y.second,gotiusa[i].second);
    }
    tate=t.first-t.second;
    yoko=y.first-y.second;
    if(tate==3) puts("B");
    else if(yoko==3) puts("C");
    else if(yoko==1&&tate==1)puts("A");
    else if(tate==2&&yoko==1){
        int a = 0,b = 0;
        rep(i,gotiusa.size()){
            if(t.first==gotiusa[i].first)a=gotiusa[i].second;
            else if(t.second==gotiusa[i].first)b=gotiusa[i].second;
        }
            (a>b ? puts("D"):puts("F"));
    }
    else if(tate==1&&yoko==2){
        int a = 0,b = 0;
        rep(i,gotiusa.size()){
            if(y.first==gotiusa[i].second)a=gotiusa[i].first;
            else if(y.second==gotiusa[i].second)b=gotiusa[i].first;
        }
            (a>b ? puts("E"):puts("G"));
        }
    }
    return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>

using namespace std;

bool one(const vector<string> &v, int x, int y) {
    if(x < 0 || y < 0 || x >= v[0].size() || y >= v.size()) return false;
    return v[y][x] == '1';
}

int main() {
    vector<string> v(8);
    while(cin >> v[0]) {
        for(int i = 1; i < 8; ++i) cin >> v[i];

        char kind;
        for(int y = 0; y < 8; ++y) {
            for(int x = 0; x < 8; ++x) {
                if(one(v, x, y)) {
                    if(one(v, x+1, y) && one(v, x, y+1) && one(v, x+1, y+1)) kind = 'A';
                    else if(one(v, x, y+1) && one(v, x, y+2) && one(v, x, y+3)) kind = 'B';
                    else if(one(v, x+1, y) && one(v, x+2, y) && one(v, x+3, y)) kind = 'C';
                    else if(one(v, x, y+1) && one(v, x-1, y+1) && one(v, x-1, y+2)) kind = 'D';
                    else if(one(v, x+1, y) && one(v, x+1, y+1) && one(v, x+2, y+1)) kind = 'E';
                    else if(one(v, x, y+1) && one(v, x+1, y+1) && one(v, x+1, y+2)) kind = 'F';
                    else if(one(v, x+1, y) && one(v, x, y+1) && one(v, x-1, y+1)) kind = 'G';
                    goto end;
                }
            }
        }
end:
        cout << kind << endl;
    }
    return 0;
}

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

int main(){
	string s, ss;
	int v[8][8];
	while(cin >> s){
		int sx = -1, sy = -1;
		if(s[0] == '\n')cin >> s;
		for(int i = 0;i < 8;i++)v[0][i] = s[i]-'0';
		for(int i = 1;i < 8;i++){
			cin >> s;
			for(int j = 0;j < 8;j++)v[i][j] = s[j] - '0';
		}
		
		for(int i = 0;i < 8&&sx==-1;i++){
			for(int j = 0;j < 8&&sx==-1;j++){
				if(v[i][j]){sy = i;sx = j;}
			}
		}
		
		char ans = 'a';
		if(sx<7 && v[sy][sx+1]){//A,C,E,G
			if(sx<6){
				if(v[sy][sx+2])ans = 'C';
				else if(sy<7&&v[sy+1][sx+2])ans = 'E';
			}
			if(0<sx && sy<7 && v[sy+1][sx-1])ans = 'G';
			if(ans == 'a')ans = 'A';
		}else{
			if(0<sx && v[sy+1][sx-1])ans = 'D';
			if(sx<7 && v[sy+1][sx+1])ans = 'F';
			if(ans == 'a')ans = 'B';
		}
		cout << ans << endl;
	}
	return 0;
}