#include<bits/stdc++.h>
using namespace std;
int n,m,p;
vector<pair<int,int>>g[200005];
long long f0[200005],f1[200005];
void dfs0(int x,int la,int c2){
	int d=0;
	long long ff=0;
	vector<long long>vc;
	for(auto pi:g[x]){
		++d;int cu=pi.first,cc=pi.second;
		if(cu==la)continue;
		dfs0(cu,x,cc);ff+=f0[cu];
		vc.emplace_back(f1[cu]-f0[cu]);
	}
	sort(vc.begin(),vc.end(),greater<long long>());
	f0[x]=ff;f1[x]=ff+1ll*d*(d-1)*p-c2;
	int sz=vc.size();
	__int128 he=0;
	for(int i=0;i<sz;++i){
		he+=vc[i];
		f0[x]=max((__int128)f0[x],he+1ll*(i+1)*(d-i-1)*d*p+ff);
		if(la)f1[x]=max((__int128)f1[x],he-c2+1ll*(i+2)*(d-i-2)*d*p+ff);
	}
}
int main(){
	scanf("%d%d%d",&n,&m,&p);
	for(int i=1;i<=m;++i){
		int u,v,w;
		scanf("%d%d%d",&u,&v,&w);w*=2;
		g[u].emplace_back(v,w);
		g[v].emplace_back(u,w);
	}
	if(m==n-1){
		dfs0(1,0,0);
		printf("%lld\n",f0[1]/2);
		return 0;
	}
	return 0;
}