#include <bits/stdc++.h>
#include <stdio.h>
#include <stack>
#include <algorithm>
#include <string.h>
#include <vector>using namespace std;const int Maxn = 1000 +10;int A[Maxn][Maxn];int pre[Maxn<<1];
bool iscut[Maxn];
int bccno[Maxn];
int dfs_clock;
int bcc_cnt;vector <int> G[Maxn],bcc[Maxn];struct Edge
{int u,v;Edge(int u=0,int v=0) : u(u),v(v) {}
};stack <Edge> S;int dfs(int u, int fa)
{int lowu = pre[u] = ++dfs_clock;int child = 0;for(int i = 0; i < G[u].size(); i++){int v = G[u][i];Edge e = (Edge){u,v};if(!pre[v]){S.push(e);child++;int lowv = dfs(v, u);lowu = min(lowu, lowv);if(lowv >= pre[u]){iscut[u] = true;bcc_cnt++;bcc[bcc_cnt].clear();for(;;){Edge x = S.top();S.pop();if(bccno[x.u] != bcc_cnt){bcc[bcc_cnt].push_back(x.u);bccno[x.u] = bcc_cnt;}if(bccno[x.v] != bcc_cnt){bcc[bcc_cnt].push_back(x.v);bccno[x.v] = bcc_cnt;}if(x.u == u && x.v == v) break;}}}else if(pre[v] < pre[u] && v != fa){S.push(e);lowu = min(lowu, pre[v]);}}if(fa < 0 && child == 1) iscut[u] = 0;return lowu;
}void find_bcc(int n)
{memset(pre, 0, sizeof(pre));memset(iscut, 0, sizeof(iscut));memset(bccno, 0, sizeof(bccno));dfs_clock = bcc_cnt = 0;for(int i = 0; i < n; i++)if(!pre[i]) dfs(i, -1);
}int odd[Maxn], color[Maxn];
bool bipartite(int u, int b)
{for(int i = 0; i < G[u].size(); i++){int v = G[u][i];if(bccno[v] != b) continue;if(color[v] == color[u]) return false;if(!color[v]){color[v] = 3 - color[u];if(!bipartite(v, b)) return false;}}return true;
}int main()
{int  n, m;while(scanf("%d%d", &n, &m) == 2 && n){for(int i = 0; i < n; i++) G[i].clear();memset(A, 0, sizeof(A));for(int i = 0; i < m; i++){int u, v;scanf("%d%d", &u, &v);u--;v--;A[u][v] = A[v][u] = 1;}for(int u = 0; u < n; u++)for(int v = u+1; v < n; v++)if(!A[u][v]){G[u].push_back(v);G[v].push_back(u);}find_bcc(n);memset(odd, 0, sizeof(odd));for(int i = 1; i <= bcc_cnt; i++){memset(color, 0, sizeof(color));for(int j = 0; j < bcc[i].size(); j++)bccno[bcc[i][j]] = i;int u = bcc[i][0];color[u] = 1;if(!bipartite(u, i)){for(int j = 0; j < bcc[i].size(); j++)odd[bcc[i][j]] = 1;}}int ans = n;for(int i = 0; i < n; i++)if(odd[i])ans--;printf("%d\n", ans);}return 0;
}