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input/Datatahti201641.java:42: error: variable a is already defined in method main(String[])
            int a=io.nextInt();
                ^
input/Datatahti201641.java:57: error: variable a is already defined in method main(String[])
                int a=(Integer) b;
                    ^
input/Datatahti201641.java:75: error: variable a is already defined in method main(String[])
                int a= (Integer) c;
                    ^
Note: input/Datatahti201641.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
3 errors

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */


/**
 *
 * @author alexey
 */
import java.util.*; 

public class Datatahti201641 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner a=new Scanner(System.in);
        IO io =new IO();
        
        int city=io.nextInt();
        int connect=io.nextInt();
        long[][] cities = new long[city+1][2];
        int i=1;
        while(i<city+1){
            cities[i][0]=Long.MAX_VALUE;
            cities[i][1]=Long.MAX_VALUE;
            i++;
        }
        cities[1][0]=0;
        cities[1][1]=0;
      ArrayList<ArrayList<int[]>> connections= new  ArrayList<ArrayList<int[]>>();
      connections.add(new ArrayList());
        for (int j = 0; j < city; j++) {
            connections.add(new ArrayList<int[]>());
        }
        
        for (int j = 0; j < connect; j++) {
            int a=io.nextInt();
            int b=io.nextInt();
            int c=io.nextInt();
            int[] d =new int[2];
            d[0]=b;
            d[1]=c;
            connections.get(a).add(d);
        }
     
        Set check = new HashSet();
        Set check2 = new HashSet();
        
        check.add(1);
        while(true){
            for(Object b:check){
                int a=(Integer) b;
                for(int[] k:connections.get(a)){
                    long x=cities[k[0]][0];
                    long y=k[1]+cities[a][1];
                    
                    if(x>y){
                        check2.add(k[0]);
                        cities[k[0]][0]=y;
                    }
                }
            }
            check.clear();
            if(check2.isEmpty()){
                break;
            }
          
            
            for(Object c:check2){
                int a= (Integer) c;
                for(int[] k:connections.get(a)){
                    long x=cities[k[0]][1];
                    long y=cities[a][0];
                    if(x>y){
                        check.add(k[0]);
                        cities[k[0]][1]=y;
                    }
                }
            }
            
        if(check.isEmpty()){
                break;
            }
            check2.clear();
        }
        
        io.println(Math.min(cities[city][0], cities[city][1]));
       io.close();
    }
    
}