public static boolean contingiousSub(int [] a,int num){
          int sum = 0,start=0;
          for(int k=0;k<a.length;k++){
              sum+= a[k];
              while(sum>num){
                  sum-=a[start];
                  start++;
              }
              if(sum==num)
                  return true;
          }
          return false;
      }