#include #include #include #include using namespace std; int main() { int n,ai,m; cin >> n;//聚会的人数； cin >> ai;//小A的编号； cin >> m;//相互认识的数目 std::map<int,vector> mindex; for(int i=0;i<m;i++) { int key,value; char chs; cin >> key >>chs>>value; vector vkey; vector vvalue;

    if(mindex.find(key) != mindex.end())
     mindex[key].push_back(value);
    else
    {
        vkey.push_back(value);
        mindex.insert(map<int,vector<int>>::value_type(key,vkey));
        }
    
            if(mindex.find(value) != mindex.end())
     mindex[value].push_back(key);
    else
    {
        vvalue.push_back(key);
        mindex.insert(std::map<int,vector<int>>::value_type(value,vvalue));
        }
}
vector<int> vai = mindex[ai];
int nbegin =0;
int nafter =vai.size();
int nai =vai.size();
int ncn = 1;
while(ncn < n)
{
    
    for(int i=nbegin;i<nafter;i++)
    {
        int ni= vai[i];
        vector<int> vi = mindex[ni];
        for(int j=0;j<vi.size();j++)
        {
            int k = vi[j];
            if((k!=ai) && (std::find(vai.begin(),vai.end(),k) == vai.end()))
                vai.push_back(k);
        }
        }
  ncn++;
    nbegin = nafter;
    nafter = vai.size();
    if(nafter==n-1)
        break;
}

std::cout << (vai.size() -nai ) << endl; }