Go: package main

import (
	"strconv"
	"fmt"
	"bufio"
	"os"
)
const INF = 1 << 21
var scanner = bufio.NewScanner(os.Stdin)

func nextInt() int {
	scanner.Scan()
	i, e := strconv.Atoi(scanner.Text())
	if e != nil {
		panic(e)
	}
	return i
}


func main() {
	scanner.Split(bufio.ScanWords)
	n := nextInt()
	adj := make([][]int, n)
	for i := range adj {
		adj[i] = make([]int, n)
	}

	for i := 0;i < n; i++ {
		u := nextInt()
		k := nextInt()
		for j := 0; j < k; j++ {
			v := nextInt()
			c := nextInt()
			adj[u][v] = c
		}
	}

	// for i := range adj {
	// 	fmt.Println(adj[i])
	// }

	dist := make([]int, n)
	prev := make([]int, n)
	visited := make([]bool, n)
	dijkstra := func(start int, size int) {
		for i := 0; i < size; i++ {
			dist[i] = INF
			prev[i] = -1
			visited[i] = false
		}
		dist[start] = 0
		for {
			u := -1
			tmp_min := INF
			for i := 0; i < size; i++ {
				if visited[i] == false && dist[i] < tmp_min {
					tmp_min = dist[i]
					u = i
				}
			}
			if u == -1 {
				break
			}
			visited[u] = true
			for i := 0; i < size; i++ {
				if adj[u][i] > 0 {
					w := adj[u][i]
					newlen := dist[u] + w
					if newlen < dist[i] {
						dist[i] = newlen
						prev[i] = u
					}
				}
			}
		}
	}
	dijkstra(0, n)
	for i, cost := range dist {
		fmt.Printf("%d %d\n", i, cost)
	}
}

C++: #include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

const int INF = (1 << 30) - 1;
const ll INF64 = ((ll)1 << 62) - 1;
const double PI = 3.1415926535897932384626433832795;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { -1, 0, 1, 0 };

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	int n;
	cin >> n;

	vector<vector<pair<int, int>>> g(n);
	for (int i = 0; i < n; i++) {
		int k, v;
		cin >> k >> v;
		for (int j = 0; j < v; j++) {
			int u, c;
			cin >> u >> c;
			g[k].emplace_back(u, c);
		}
	}

	priority_queue<int> pq;
	pq.emplace(0);

	vector<int> dist(n, INF);
	dist[0] = 0;
	vector<bool> used(n);
	while (!pq.empty()) {
		int u = pq.top(); pq.pop();

		if (used[u]) {
			continue;
		}

		used[u] = true;
		for (auto e : g[u]) {
			int next = e.first;
			int cost = e.second;
			if (dist[next] > dist[u] + cost) {
				dist[next] = dist[u] + cost;
				pq.emplace(next);
			}
		}
	}

	for (int i = 0; i < n; i++) {
		cout << i << " " << dist[i] << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<climits>
#include<vector>
#include<list>
#include<functional>
#include<algorithm>
#include<string>
#include<cmath>
#include<complex>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<deque>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) for(int i=0;i<(n);i++)
#define INF (int)1e9
#define INFL (ll)1e11
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

void dijkstra(vector<vector<int>> v, vector<vector<int>> c, vector<int> &d) {
	d[0] = 0;
	priority_queue<P, vector<P>, greater<P>> pq;
	pq.push(P(0, 0));
	while (!pq.empty()) {
		int s = pq.top().second;
		int dis = pq.top().first;
		pq.pop();
		if (dis > d[s]) continue;
		REP(j, v[s].size()) {
			int u = v[s][j];
			int w = c[s][j];
			if (d[u] > d[s] + w) {
				d[u] = d[s] + w;
				pq.push(P(d[u], u));
			}
		}
	}
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int n;
	cin >> n;
	vector<vector<int>> v(n), c(n);
	REP(i, n) {
		int u, k;
		cin >> u >> k;
		v[u] = vector<int>(k);
		c[u] = vector<int>(k);
		REP(j, k) cin >> v[u][j] >> c[u][j];
	}
	vector<int> d(n, INF);
	dijkstra(v, c, d);
	REP(i, n) {
		cout << i << " " << d[i] << "\n";
	}
	
	return 0;
}

C++: #include<stdio.h>

#define MAX 500
static const int INFTY = (1<<21);
 
int main(){
  int n, i, j, e, sum,k,a,v1;
  int key,p[MAX],v[MAX],u,c[MAX],m[MAX][MAX];
   
  scanf("%d", &n);
  for ( i = 0; i< n; i++ ){
    for ( j = 0; j < n; j++ ){
      m[i][j] = INFTY;
    }
  }
   
  for ( i = 0; i < n; i++ ){
    scanf("%d %d", &u, &k);
    for ( j = 0; j < k; j++ ){
      scanf("%d %d", &v1, &a);
      m[u][v1] = a;
    }
  }
  for(i=0;i<n;i++){
    c[i]=INFTY;
    p[i]=-1;
    v[i]=0;
  }
  c[0]=0;
 
  while(1){
    key=INFTY;
    u=-1;
    for(i=0;i<n;i++){
      if(key>c[i] && !v[i]){
    u=i;
    key=c[i];
      }
    }
    if(u==-1)break;
    v[u]=1;
    for(j=0;j<n;j++){
      if(m[u][j]+c[u]<c[j] && !v[j]){
    p[j]=u;
    c[j]=c[u]+m[u][j];
      }
    }
  }
   
  for ( i = 0; i < n; i++ ){
    printf("%d %d\n", i, (c[i]==INFTY?-1:c[i]));
  }
   
  return 0;
}

C++: // #include <bits/stdc++.h>
// using namespace std;
// #define rep(i, n) for (int i = 0; i < n; i++)

// int n;
// vector<vector<int>> a(100,vector<int>(100, -1)); // 各頂点間の重みを表す隣接行列
// vector<int> d(100, -1);

// void dijkstra(int start) {
//     vector<int> s;
    
//     s.push_back(start);
//     d[start] = 0;
//     while (s.size() < n) {
//         int min_v = 10000001, min_i;
//         rep(i, s.size()) {
//             int cur = s[i];
//             rep(j, n) {
//                 int adj = a[cur][j];
//                 if (adj != -1 && d[j] == -1 && d[cur] + adj < min_v) {
//                     min_v = d[cur] + adj;
//                     min_i = j;
//                 }
//             }
//         }
//         s.push_back(min_i);
//         d[min_i] = min_v;
//     }
// }

// int main() {
//     scanf("%d", &n);
//     rep(i, n) {
//         int u, k;
//         scanf("%d %d", &u, &k);
//         rep(j, k) {
//             int v, c;
//             scanf("%d %d", &v, &c);
//             a[u][v] = c;
//         }
//     }
//     dijkstra(0);
//     rep(i, n) {
//         printf("%d %d\n", i, d[i]);
//     }
// }

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)

const int INF = 1000000000;
int n;
vector<vector<pair<int,int>>> e;
vector<int> d;
vector<bool> t;
void dijkstra(int start) {
    d[start] = 0;
    priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> pq;
    pq.push({d[start],start});
    while (not pq.empty()) {
        int u = pq.top().second; // uは最短経路木に含まれない頂点のうちd[u]が最小であるもの
        pq.pop();
        t[u] = true; // uを最短経路木に含ませる
        rep(j, e[u].size()) {
            int v = e[u][j].first; // uの隣接点
            if (t[v] == false) { // 隣接点のうち最短経路木に含まれないもの
                if (d[u] + e[u][j].second < d[v]) { // e[u][j].secondはuから隣接点までの距離
                    d[v] = d[u] + e[u][j].second;
                    pq.push({d[v],v});
                }
            }
        }
    }
}

int main() {
    cin >> n;
    e.resize(n);
    rep(i, n) {
        int u, k;
        cin >> u >> k;
        rep(j, k) {
            int v, c;
            cin >> v >> c;
            e[u].push_back({v,c});
        }
    }
    d.resize(n,INF);
    t.resize(n,false);
    dijkstra(0);
    rep(i, n) {
        printf("%d %d\n", i, d[i]);
    }
}

C++: #include <iostream>
#include <algorithm>
using namespace std;

const int INF = 1 << 29;

int main()
{
    int n,u,k,v,c;
    int V[101][101];
    fill((int*)V, (int*)(V + 101), INF);
    
    cin >> n;
    for(int i = 0; i < n; ++i){
        V[i][i] = 0;
    }
    
    for(int i = 0; i < n; ++i){
        cin >> u >> k;
        for(int j = 0; j < k; ++j){
            cin >> v >> c;
            V[u][v] = c;
        }
    }
    
    for(int k = 0; k < n; ++k){
        for(int i = 0; i < n; ++i){
            for(int j = 0; j < n; ++j){
                V[i][j] = min(V[i][j],V[i][k] + V[k][j]);
            }
        }
    }
    
    for(int i = 0; i < n; ++i){
        cout << i << ' ' << V[0][i] << endl;
    }
    
}