question: what was the total number of casualties in 2015?
table.cells: year month total
table.cells: jan feb mar apr may jun jul aug sep oct nov dec
table.cells: 2012 none none none none none none none none none none 445 230 none
table.cells: 2013 319 418 229 595 963 685 928 716 887 852 565 661 7,818
table.cells: 2014 618 564 484 610 603 1531 1186 1265 854 856 936 680 12,282
table.cells: 2015 790 611 729 535 665 665 844 585 537 559 489 506 7,515
table.cells: 2016 490 410 575 410 468 382 629 473 609 1,120 926 none 6,492