#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
const int MAX = 200020;
typedef pair < int, int > pii;
vector < pii > to[MAX];
vector < int > root, child[MAX];
int depth[MAX];
int numNode, numEdge;
void input() {
scanf("%d%d", &numNode, &numEdge);
int i;
for (i = 0; i < numEdge; i++) {
int f, s;
scanf("%d%d", &f, &s);
to[f].push_back(pii(s, i));
to[s].push_back(pii(f, i));
}
}
int parent[MAX], state, numOddCycle, evenCount[MAX], oddCount[MAX];
void initDFS(int node) {
root.push_back(node);
parent[node] = node;
depth[node] = 1;
state = 0;
numOddCycle = 0;
}
bool used[MAX];
void dfs(int node) {
for (int edge = 0; edge < to[node].size(); edge++) {
bool &visited = used[to[node][edge].second];
if (visited) continue;
visited = 1;
int next = to[node][edge].first;
if (depth[next] == 0) {
parent[next] = node;
depth[next] = depth[node]+1;
child[node].push_back(next);
dfs(next);
} else {
if ((depth[node]-depth[next])&1) {
//even cycle
evenCount[node]++;
evenCount[next]--;
} else {
//odd cycle
if (state == 0) state = 1;
else if (state == 1) state = 2;
numOddCycle++;
oddCount[node]++;
oddCount[next]--;
}
}
}
}
int countDFS(int node) {
int ret = 0;
for (int edge = 0; edge < child[node].size(); edge++) {
int next = child[node][edge];
ret += countDFS(next);
evenCount[node] += evenCount[next];
oddCount[node] += oddCount[next];
}
if (evenCount[node] == 0 && oddCount[node] == numOddCycle && parent[node] != node) ret++;
return ret;
}
int ans = 0;
bool oddCycleExist = 0;
void solve() {
for (int node = 1; node <= numNode; node++) {
if (parent[node] == 0) {
initDFS(node);
dfs(node);
int waiting = countDFS(node);
if (state == 1) {
//only one odd cycle
waiting++;
}
if (!oddCycleExist) {
if (state > 0) {
ans = waiting;
oddCycleExist = 1;
} else {
ans += waiting;
}
} else {
if (state > 0) {
ans = 0;
break;
}
}
}
}
printf("%d\n", ans);
}
int main() {
input();
solve();
return 0;
}
