import java.util.*;
import java.lang.*;
import java.io.*;
class Main
{
static boolean[][] used = new boolean[101][101];
static Scanner sc
= new Scanner
(System.
in);
{
int n, m;
n = sc.nextInt();
m = sc.nextInt();
for(int i = 0; i < m; i++){
int a, b;
a = sc.nextInt();
b = sc.nextInt();
used[a][b] = used[b][a] = true;
}
for(int i = 1; i <= n; i++){
for(int j = i+1; j <= n; j++){
if(used[i][j] == false){
return;
}
}
}
}
}
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