#include<bits/stdc++.h>
#define ll long long
#define fr(i,j,k) for(register int i=j;i<=k;++i)
#define rf(i,j,k) for(register int i=j;i>=k;--i)
#define foredge(i,j) for(register int i=head[j];i;i=e[i].nxt)
#define pb push_back
#define ldb long double
#define Times printf("Time:%.3lf\n",clock()/CLOCKS_PER_SEC)
#define pii pair<int,int>
#define mk make_pair
using namespace std;
inline int read(){
	int x=0;
	bool f=0;
	char c=getchar();
	while(!isdigit(c)) f|=(c=='-'),c=getchar();
	while(isdigit(c)) x=(x<<3)+(x<<1)+(c^48),c=getchar();
	return f?-x:x;
}
inline void write(int x){
    if(x<0){putchar('-');x=-x;}
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
inline void writeln(int x){write(x); puts("");}
inline void writepl(int x){write(x); putchar(' ');}
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
inline int randfind(int l,int r){return rnd()%(r-l+1)+l;}
//inline void init(){
//	int t=read();
//	while(t--) work();
//}
const int Maxn=2e3+10,Maxm=1e5+10;
const ldb inf=1e30;
ldb f[Maxn];
struct node{
    int pos;
    ldb dis;
    bool operator < (const node &p) const {return dis>p.dis;}
};
int n,m,T;
vector<pair<int,double> > vc[Maxn];
inline void init(){
    n=read();m=read();T=read();
    fr(i,1,m){
        int x,y,l,c;
        x=read();y=read();l=read();c=read();
        vc[x].pb(mk(y,1ll*l*c));
        vc[y].pb(mk(x,1ll*l*c));
    }
}
int vis[Maxn];
inline ldb getans(ldb x,ldb y){return x+y+2*sqrt(x*y);}
inline void work(){
    fr(i,1,n) f[i]=inf;f[1]=0;
    priority_queue<node> q;q.push((node){1,0});
    while(!q.empty()){
        node tmp=q.top();q.pop();
        int x=tmp.pos;ldb d=tmp.dis;
        if(vis[x]) continue;vis[x]=1;
        for(auto p:vc[x]){
            int y=p.first;
            // cout<<"**"<<p.first<<' '<<p.second<<endl;
            if(f[y]>getans(d,p.second)){
                f[y]=getans(d,p.second);
                if(!vis[y]) q.push((node){y,f[y]});
            }
        }
    }
    printf("%.10Lf\n",f[n]/T);
}
signed main(){
	// freopen("input.in","r",stdin);
	// freopen("output.out","w",stdout);
    init();work();
    // printf("\nTIME:%.3lf",(double)clock()/CLOCKS_PER_SEC);
	return 0;
}