/* {{{ Shinobu kawaii */
/*
  ______   __        _                  __                 
.' ____ \ [  |      (_)                [  |                
| (___ \_| | |--.   __   _ .--.   .--.  | |.--.   __   _   
 _.____`.  | .-. | [  | [ `.-. |/ .'`\ \| '/'`\ \[  | | |  
| \____) | | | | |  | |  | | | || \__. ||  \__/ | | \_/ |, 
 \______.'[___]|__][___][___||__]'.__.'[__;.__.'  '.__.'_/ 

*/
// clang-format off
/* }}} */

#include <bits/stdc++.h>
using namespace std;

// #define int long long
struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* cpp template {{{ */

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) begin(v), end(v)
#define RALL(v) rbegin(v), rend(v)
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (ll i = (a); i >= (ll)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\n';

/* alias */
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using D = double;
using P = complex<D>;
using vs = vector<string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;
const D EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in() {int x; cin >> x; return x;}
inline ll IN() {ll x; cin >> x; return x;}
inline vs split(const string& t, char c) {vs v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b) {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b) {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p) {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x) {cout << x << '\n';}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v) {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ") {REP(i, v.size()) cout << v[i] << (i != (ll)v.size() - 1 ? s : "\n");}
// clang-format on
/* }}} */

struct Edge {
  Edge() {}
  Edge(int a, int c) { to = a; cost = c; }
  int to, cost;
};

int n, k;
int c[5000], r[5000];
vi g[5000];
vector<Edge> newg[5000];

int dijkstra() {
  minPQ<pii> q;
  int d[5000];
  fill(ALL(d), INF);
  d[0] = 0;
  q.emplace(0, 0);

  while (q.size()) {
    auto p = q.top(); q.pop();
    int v = p.Se;
    if (d[v] < p.Fi) continue;
    for (auto &e : newg[v]) {
      if (d[e.to] > d[v] + e.cost) {
        d[e.to] = d[v] + e.cost;
        q.emplace(d[e.to], e.to);
      }
    }
  }
  return d[n - 1];
}

signed main() {
  cin >> n >> k;
  REP(i, n) cin >> c[i] >> r[i];
  REP(i, k) {
    int a = in() - 1, b = in() - 1;
    g[a].eb(b);
    g[b].eb(a);
  }
  REP(i, n) {
    queue<pii> q;
    bool vis[5000] = {};
    q.emplace(i, 0);
    vis[i] = true;
    while (q.size()) {
      auto t = q.front(); q.pop();
      if (t.Se >= r[i]) continue;
      for (int &e : g[t.Fi]) {
        if (vis[e]) continue;
        vis[e] = true;
        newg[i].eb(e, c[i]);
        q.emplace(e, t.Se + 1);
      }
    }
  }
  print(dijkstra());

  return 0;
}

Measured memory_bytes: 127472