Epidemie

#include <fstream>
#define N 1001
using namespace std;
int n,a[N][N],
	x[N], /// coada
	v[N], /// vizitat
    d[N]; /// distantele la varfuri
int st,dr;

int main()
{
    int i,j,m,k,p;
	ifstream f("epidemie.in");
    f>>n>>m;
    while(m--)
        f>>i>>j,a[i][j]=a[j][i]=1;
    f>>k;
	while(k--)
        f>>p,x[++dr]=p,v[p]=d[p]=1;
    f.close();
	st=1;
	while(st<=dr)
	{
		int k=x[st];
		for(int i=1;i<=n;++i)
			if(v[i]==0&&a[k][i]==1)
				++dr,v[i]=1,x[dr]=i,d[i]=d[k]+1;
		++st;
	}
	int C=0;
	for(int i=1;i<=n;++i)
		if(d[i]>C)
            C=d[i];
	ofstream g("epidemie.out");
	g<<C;
    g.close();
	return 0;
}