Go: ///
// File:  1160.go
// Author: ymiyamoto
//
// Created on Sun Mar  4 20:45:57 2018
//
package main

import (
	"fmt"
)

var w, h int
var graph [][]string

func dfs(visited [][]bool, x, y int) {
	visited[x][y] = true

	for i := -1; i <= 1; i++ {
		for j := -1; j <= 1; j++ {
			dx := x + i
			dy := y + j
			if 0 <= dx && dx < h && 0 <= dy && dy < w && graph[dx][dy] == "1" && !visited[dx][dy] {
				dfs(visited, dx, dy)
			}
		}
	}
}

func main() {
	for {
		fmt.Scan(&w, &h)
		if w == 0 && h == 0 {
			break
		}

		graph = make([][]string, h)
		for i := range graph {
			graph[i] = make([]string, w)
		}

		for i := 0; i < h; i++ {
			for j := 0; j < w; j++ {
				var s string
				fmt.Scan(&s)
				graph[i][j] = s
			}
		}

		visited := make([][]bool, h)
		for i := range visited {
			visited[i] = make([]bool, w)
		}

		count := 0
		for i := range graph {
			for j := range graph[i] {
				if graph[i][j] == "1" && !visited[i][j] {
					dfs(visited, i, j)
					count++
				}
			}
		}

		fmt.Println(count)
	}
}

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

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define bit(n) (1LL<<(n))
// functions
template <typename T> void unique(T& c){c.erase(std::unique(c.begin(), c.end()), c.end());}
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

typedef struct UnionFind_ {
  vector<int> par, rank_, siz;
  UnionFind_(){}
  explicit UnionFind_(int n): rank_(n, 0), siz(n, 1) {
    par.resize(n);
    for(int i = 0; i < n; i++)par[i] = i;
  }
  int find(int x) {
    if(par[x] == x)return x;
    else return par[x] = find(par[x]);
  }
  bool same(int x, int y) {
    if(find(x) == find(y))return true;
    else return false;
  }
  bool unite(int x, int y){
    int xp = find(x);
    int yp = find(y);
    if(xp == yp)return false;
    if(rank_[xp] > rank_[yp]){
      par[yp] = xp;
      siz[xp] += siz[yp];
    }
    else if(rank_[xp] < rank_[yp]){
      par[xp] = yp;
      siz[yp] += siz[xp];
    }
    else {
      par[yp] = xp;
      siz[xp] += siz[yp];
      rank_[xp]++;
    }
    return true;
  }
  int size(int i){
    return siz[find(i)];
  }
} UnionFind;

int c[101][101];

int main(int argc, char const* argv[])
{
  int w, h;
  while(true){
    cin >> w >> h;
    if(w == 0 && h == 0)break;
    rep(i, h){
      rep(j, w)cin >> c[i][j];
    }
    UnionFind uf(w * h);
    rep(i, h){
      rep(j, w){
        if(!c[i][j])continue;
        for(int k = -1; k <= 1; k++){
          for(int l = -1; l <= 1; l++){
            if(k == 0 && l == 0)continue;
            int nx = i + k, ny = j + l;
            if(nx >= 0 && nx < h && ny >= 0 && ny < w && c[nx][ny]){
              uf.unite(i * w + j, nx * w + ny);
            }
          }
        }
      }
    }
    int res = 0;
    rep(i, h * w){
      if(c[i/w][i%w] && uf.find(i) == i)++res;
    }
    cout << res << endl;
  }
  return 0;
}

C++: 
#include <set>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <cmath>
#include <ctype.h>
#include <ctime>
#include <cstdio>
#include <vector>
#include <string>
#include <bitset>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <numeric>
#include <complex>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <cassert>
#include <iostream>
#include <iterator>
#include <algorithm>

using namespace std;

#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define lengthof(x) (sizeof(x) / sizeof(*(x)))
#define FILL(ptr, value) FILL_((ptr), sizeof(ptr)/sizeof(value), (value))
template <typename T>
void FILL_(void * ptr, size_t size, T value){
  std::fill((T*)ptr, (T*)ptr+size, value);
}
//4方向ベクトル→↑←↓
int dx[] ={1,0,-1,0};
int dy[] ={0,-1,0,1};
int w,h;
int board[55][55];
int ans;

void dfs(int y,int x){
  board[y][x] =0;
  for(int i = -1;i <=1;i++){
    for(int j = -1;j <=1;j++){
      int ny =y + i;
      int nx =x + j;
      if(nx >=1&&nx <=w&&ny >=1&& ny <=h&&board[ny][nx] ==1){
	dfs(ny,nx);
      }
    }
  }
}

int main()
{
  
  while(cin>>w>>h,w||h){
    ans = 0;
    for(int i = 1;i <=h;i++){
      for(int j = 1;j <=w;j++){
	cin>>board[i][j];
      }
    }
    for(int i = 1; i <=h;i++){
      for(int j = 1;j <=w;j++){
	if(board[i][j] ==1){
	  ans++;
	  dfs(i,j);
	}
      }
    }
    cout <<ans<<endl;
  }
  return 0;
}