Compilare: main.cpp:2:175: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type] 2 | using k=int;using namespace std;ifstream f("dfs.in");ofstream g("dfs.out");k n,m;vector<k>v[100001];k z[100001];void dfs(k x){z[x]=1;for(k&y:v[x]){if(!z[y]){z[y]=1;dfs(y);}}}main(){f>>n>>m;for(k x,y;m;--m){f>>x>>y;v[x].push_back(y);v[y].push_back(x);}k c=0;for(k i=1;i<=n;++i){if(z[i])continue;dfs(i);c++;}g<<c;} | ^~~~