#include<stdio.h>

#define input "dfs.in"
#define output "dfs.out"

#define dim 5000

void DF(int vf);

int n, m, a[dim][dim], s[dim];

int main()
{
	FILE *in, *out;

	in = fopen (input, "r");
	out = fopen (output, "w");

	fscanf(in, "%d%d", &n, &m);

	int i, j, x, y;

	for(i=1; i<=m; i++)
	{
		fscanf(in, "%d%d", &x, &y);

		a[x][y] = a[y][x] = 1;

	}

	int ok=0, cont=0;


	for(i=1; i<=n; i++)
	{
		if(s[i]!=-1)
		{
			DF(i);

			for(j=1; j<=n; j++)

				if(s[j]==-1)
				{
					ok = 1;


				}

		}

		if(ok==1)

			cont++;

		ok = 0;

	}


	fprintf(out, "%d", cont);

	return 0;

}

void DF(int vf)
{
	int k;

	s[vf] = -1;


	for(k=1; k<=n; k++)

		if((a[vf][k] == 1) && (s[k] == 0))

			DF(k);

}