#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cassert>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <utility>
#include <numeric>
#include <algorithm>
#include <bitset>
#include <complex>
using namespace std;
const int LIM_N = 100000;
const int LIM_M = 200000;
int N, M;
int A[LIM_M + 10], B[LIM_M + 10];
int m, ptr[LIM_N + 10], next[LIM_M * 2 + 10], zu[LIM_M * 2 + 10];
int ips[LIM_N + 10], depths[LIM_N + 10];
int badCnt, goodCnt;
int bad[LIM_N + 10], good[LIM_N + 10];
void dfs0(int u, int ip, int depth) {
int i, v;
ips[u] = ip;
depths[u] = depth;
for (i = ptr[u]; ~i; i = next[i]) if ((i ^ 1) != ip) {
v = zu[i];
if (!~depths[v]) {
// tree edge
dfs0(v, i, depth + 1);
} else if (depths[u] > depths[v]) {
// back edge
if (depths[u] % 2 == depths[v] % 2) {
++badCnt;
++bad[u];
--bad[v];
} else {
++goodCnt;
++good[u];
--good[v];
}
}
}
}
void dfs1(int u, int ip) {
int i, v;
for (i = ptr[u]; ~i; i = next[i]) if ((i ^ 1) != ip) {
v = zu[i];
if (i == ips[v]) {
dfs1(v, i);
bad[u] += bad[v];
good[u] += good[v];
}
}
}
int main() {
int i, u;
for (; ~scanf("%d%d", &N, &M); ) {
for (i = 0; i < M; ++i) {
scanf("%d%d", &A[i], &B[i]);
--A[i];
--B[i];
}
m = 0;
memset(ptr, ~0, N * 4);
for (i = 0; i < M; ++i) {
next[m] = ptr[A[i]]; ptr[A[i]] = m; zu[m] = B[i]; ++m;
next[m] = ptr[B[i]]; ptr[B[i]] = m; zu[m] = A[i]; ++m;
}
memset(ips, ~0, N * 4);
memset(depths, ~0, N * 4);
badCnt = 0;
goodCnt = 0;
memset(bad, 0, N * 4);
memset(good, 0, N * 4);
for (u = 0; u < N; ++u) if (!~depths[u]) {
dfs0(u, -1, 0);
}
for (u = 0; u < N; ++u) if (!~ips[u]) {
dfs1(u, -1);
}
int ans = 0;
// tree edge
for (u = 0; u < N; ++u) if (~ips[u]) {
if (bad[u] == badCnt && good[u] == 0) {
++ans;
}
}
// back edge
if (badCnt == 1) {
++ans;
}
printf("%d\n", ans);
}
return 0;
}
