C programming error.2Darrays

I have the code below.The problem is that I am taking a two dimensional array with a rows and 2 col.The 1st col is for storing values and 2nd as a flag.The problem arises when I initialize my flag the values are also getting affected.

#include<stdio.h>
    int main()
    {
        int a,b;
        scanf("%d%d",&a,&b);
        int arr[a][1];
        int i,j,k,sum=0;

        for(i=0;i<a;i++)
        {

            scanf("%d",&arr[i][0]);
        }
        for(i=0;i<a;i++)
        {

            printf("%d\n",arr[i][0]);
        }

        for(j=0;j<a;j++)
        {

           arr[j][1]=0;
        }
     for(i=0;i<a;i++)
        {

            printf("%d\n",arr[i][0]);//Different Values
        }
    }