#include <iostream>
#include <stack>
using namespace std;
int main() {int a,b,c,d,e,f,i,k,n;stack<int> q,r;cin>>n>>k>>a>>b;stack<int>* j[n+1];
for(i=1;i<=n;i++)j[i]=new stack<int>;int* m=new int[n+1];int* l=new int[n+1];
for(i=0;i<k;i++){cin>>f>>c;j[f]->push(c);j[c]->push(f);}if(a==b){cout<<a;return 0;}
if(a<b){if(j[1]->empty()){cout<<b;return 0;}m[1]=1;for(i=2;i<=n;i++)m[i]=0;e=a;
while(!j[1]->empty()){c=j[1]->top();j[1]->pop();m[c]=1;if(c==n){cout<<a;return 0;}
r.push(c);}while(!r.empty()){swap(q,r);e=e+a;if(e>=b){cout<<b;return 0;}
while(!q.empty()){f=q.top();q.pop();while(!j[f]->empty()){c=j[f]->top();j[f]->pop();
if(m[c]==0){if(c==n&&e<b){cout<<e;return 0;}m[c]=1;r.push(c);}}}}cout<<b;return 0;}
else{if(j[1]->empty()){cout<<b;return 0;}m[1]=1;e=b;for(i=2;i<=n;i++){l[i]=0;}
while(!j[1]->empty()){c=j[1]->top();j[1]->pop();l[c]=1;}if(!l[n]){cout<<b;return 0;}
for(i=2;i<=n;i++){if(l[i]==0){r.push(i);m[i]=1;}else m[i]=0;l[i]=0;}while(!r.empty()){
swap(q,r);e=e+b;if(e>=a){cout<<a;return 0;}d=0;while(!q.empty()){f=q.top();q.pop();d++;
while(!j[f]->empty()){c=j[f]->top();j[f]->pop();l[c]++;}}if(l[n]<d&&e<a){cout<<e;
return 0;}for(i=2;i<=n;i++){if(l[i]<d&&m[i]==0){m[i]=1;r.push(i);}l[i]=0;}}cout<<a;
return 0;}}