Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
type Node struct {
	cost int
	done bool
}

type Edge struct {
	to, cost int
}

const INF = 1 << 60

func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	nodes := make([]Node, N)
	for i := 0; i < N; i++ {
		nodes[i].cost = INF
	}
	E := make([][]Edge, N)
	for i := 0; i < N; i++ {
		id, k := sc.nextInt(), sc.nextInt()
		for j := 0; j < k; j++ {
			to, cost := sc.nextInt(), sc.nextInt()
			E[id] = append(E[id], Edge{to, cost})
		}
	}
	nodes[0].cost = 0
	for {
		cur := 0
		minCost := INF
		for i := 0; i < N; i++ {
			n := nodes[i]
			if !n.done && n.cost < minCost {
				cur = i
				minCost = n.cost
			}
		}
		if minCost == INF {
			break
		}
		nodes[cur].done = true
		for i := 0; i < len(E[cur]); i++ {
			to, cost := E[cur][i].to, E[cur][i].cost+nodes[cur].cost
			if !nodes[to].done && cost < nodes[to].cost {
				nodes[to].cost = cost
			}
		}
	}

	for i := 0; i < N; i++ {
		fmt.Fprintln(wtr, i, nodes[i].cost)
	}
	wtr.Flush()
}

C++: #define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;

//#define int long long
#define DBG 1
#define dump(o) if(DBG){cerr<<#o<<" "<<o<<endl;}
#define dumpc(o) if(DBG){cerr<<#o; for(auto &e:(o))cerr<<" "<<e;cerr<<endl;}
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define each(it,c) for(auto it=(c).begin();it!=(c).end();it++)
#define all(c) c.begin(),c.end()
const int INF = sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = (int)(1e9 + 7);
const int W = 0; const int B = 1;
int n;
vector<vector<pair<int, int>>>M;
void dijkstra() {
	int minv;
	vector<int>d(n, INF), color(n, W);
	d[0] = 0;
	while (1) {
		minv = INF;
		int u = -1;
		rep(i, 0, n) {
			if (color[i] != B&&d[i] < minv) {
				u = i;
				minv = d[i];
			}
		}
		if (u == -1)break;
		color[u] = B;
		rep(v, 0, M[u].size()) {
			pair<int, int>t(M[u][v]);
			if (color[t.first] != B&&d[u] + t.second < d[t.first]) {
				d[t.first] = d[u] + t.second;
			}
		}
	}
	rep(i, 0, n) {
		cout << i << " " << d[i] << endl;
	}
}
signed main() {
	cin >> n; M = vector<vector<pair<int, int>>>(n, vector<pair<int, int>>());
	rep(i, 0, n) {
		int u, k; cin >> u >> k;
		rep(j, 0, k) {
			int v, c; cin >> v >> c;
			M[u].push_back(make_pair(v, c));
		}
	}
	dijkstra();
	return 0;
}

C++: /*
 * b.cc: 
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>

using namespace std;

/* constant */

const int MAX_N = 100;
const int INF = 1 << 30;

/* typedef */

typedef pair<int,int> pii;
typedef vector<pii> vpii;

/* global variables */

vpii nbrs[MAX_N];
int dists[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  cin >> n;

  for (int i = 0; i < n; i++) {
    int u, k;
    cin >> u >> k;
    for (int j = 0; j < k; j++) {
      int v, c;
      cin >> v >> c;
      nbrs[u].push_back(pii(v, c));
    }
  }

  for (int i = 0; i < n; i++) dists[i] = INF;
  dists[0] = 0;

  priority_queue<pii> q;
  q.push(pii(0, 0));

  while (! q.empty()) {
    pii u = q.top(); q.pop();
    int ud = -u.first, &ui = u.second;
    if (dists[ui] != ud) continue;

    vpii& nbru = nbrs[ui];
    for (vpii::iterator vit = nbru.begin(); vit != nbru.end(); vit++) {
      int &vi = vit->first, vd = ud + vit->second;
      if (dists[vi] > vd) {
	dists[vi] = vd;
	q.push(pii(-vd, vi));
      }
    }
  }

  for (int i = 0; i < n; i++) printf("%d %d\n", i, dists[i]);

  return 0;
}

C++: #include <bits/stdc++.h>
#include <string.h>
#include <cmath>
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define max3(A,B,C) max((A),max((B),(C)))
#define popcount(X) __builtin_popcount(X)
#define popcountl(X) __builtin_popcountl(X)
#define getbit(x,i) (1&((x)>>(i)))
#define setbit(x,i,bit) ((x)|=((bit)<<(i)))
#define getbitl(x,i) (1&((x)>>((ll)i)))
#define setbitl(x,i,bit) ((x)|=((bit)<<((ll)i)))
#define log2(x) (32 - __builtin_clz(x))
#define log2l(x) (32 - __builtin_clzl(x))

using namespace std;

typedef long long int ll;
typedef unsigned long long int ull;
typedef pair<ll,ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef vector<vii> vvii;

const int INF = 0x3f3f3f3f;
const long long int INFL = 0x3f3f3f3f3f3f3f3f;
const double pi = atan(1.0)*4.0;
const int N = 3e5 + 500;

int dist[N], mrc[N];
vii v[N];
set<ii> st;

void Dijkstra(int o) {
	memset(dist,INF,sizeof(dist));
	dist[o] = 0;
	st.clear();
	st.insert(mp(0,o));
	memset(mrc,0,sizeof(mrc));
	while(!st.empty()) {
		set<ii>::iterator it = st.begin();
		if(mrc[it->s] == 0) {
			mrc[it->s] = 1;
			dist[it->s] = it->f;
			for(int i = 0; i < v[it->s].size(); i++) {
				st.insert(mp(dist[it->s] + v[it->s][i].s,v[it->s][i].f));
			}
		}
		st.erase(it);
	}
}

int main(void) {
	int n;
	
	scanf("%d", &n);
	
	for(int i = 0; i < n; i++) {
		int u, k;
		scanf("%d %d", &u, &k);
		for(int j = 0; j < k; j++) {
			int vt, c;
			scanf("%d %d", &vt, &c);
			v[u].pb(mp(vt,c));
		}
	}
	Dijkstra(0);
	for(int i = 0; i < n; i++) {
		printf("%d %d\n", i, dist[i]);
	}
	
	return 0;
}

C++: #include <queue>
#include <algorithm>
#include <cstdio>
#define INF 100000000
//#define MAX_E 100
#define MAX_V 105
using namespace std;

struct edge{int to, cost;};
typedef pair<int,int> P;

int V; //????????°
vector<edge> G[MAX_V];
int d[MAX_V];

void dijkstra(int s){
  priority_queue<P,vector<P>,greater<P> > que;
  fill(d,d+V,INF);
  d[s]=0;
  que.push(P(0,s));
  while(!que.empty()){
    P p=que.top();que.pop();
    int v=p.second;
    if(d[v]<p.first)continue;
    for(int i=0;i<G[v].size();i++){
      edge e=G[v][i];
      if(d[e.to]>d[v]+e.cost){
        d[e.to]=d[v]+e.cost;
        que.push(P(d[e.to],e.to));
      }
    }
  }
}

int main(){
  int n,u,k;
  edge e;
  scanf("%d",&n);
  V=n;
  for(int i=0;i<n;i++){
    scanf("%d%d",&u,&k);
    for(int j=0;j<k;j++){
      scanf("%d%d",&e.to,&e.cost);
      G[u].push_back(e);
    }
  }
  dijkstra(0);
  for(int i=0;i<n;i++){
    printf("%d %d\n",i,d[i]);
  }
  return 0;
}