// p is parent

// s is source

// adj is adjacency list representation of graph

// path is to store cycle and is a set

// ch is children/neighbor of s;

bool dfs(ll s,ll p)

{

visited[s]=true;

for(auto ch:adj[s])

{

    if(ch!=p&&visited[ch])

    {

        path.insert(ch);

        return true;

    }

    if(!visited[ch])

    {

        if(dfs(ch,s))

        {

            path.insert(ch);

            return true;

        }

    }

}

return false;

}