#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL,LL> PII;
const int N=1e4+10,K=105;
LL n,m,k,d[N];bool v[N];
vector<PII> G[N];
void dijkstra()
{
	memset(d,0x3f,sizeof(d));d[1]=0;
	memset(v,0,sizeof(v));
	priority_queue<PII,vector<PII>,greater<PII>> Q;Q.push({0,1});
	while(!Q.empty())
	{
		LL x=Q.top().second,t=Q.top().first; Q.pop();
		if(v[x])continue;
		v[x]=1;
		for(auto i:G[x])
		{
			LL y=i.first,w=i.second;
			LL tt=t+1 + ( t<w ? (w-t+k-1)/k*k : 0);
			if(d[y]>tt)
			{
				d[y]=tt;
				Q.push({tt,y});
			}
		}
	}
}
int main()
{
	scanf("%lld%lld%lld",&n,&m,&k);
	for(LL i=1,x,y,w;i<=m;i++)scanf("%lld%lld%lld",&x,&y,&w),G[x].push_back({y,w});
	dijkstra();
	printf("%lld\n",(v[n]==1) ? d[n] : -1 );
	return 0;
}