"rivers" <-
c(735, 320, 325, 392, 524, 450, 1459, 135, 465, 600, 330, 336, 280, 315, 
870, 906, 202, 329, 290, 1000, 600, 505, 1450, 840, 1243, 890, 350, 407, 
286, 280, 525, 720, 390, 250, 327, 230, 265, 850, 210, 630, 260, 230, 360, 
730, 600, 306, 390, 420, 291, 710, 340, 217, 281, 352, 259, 250, 470, 680, 
570, 350, 300, 560, 900, 625, 332, 2348, 1171, 3710, 2315, 2533, 780, 280, 
410, 460, 260, 255, 431, 350, 760, 618, 338, 981, 1306, 500, 696, 605, 
250, 411, 1054, 735, 233, 435, 490, 310, 460, 383, 375, 1270, 545, 445, 
1885, 380, 300, 380, 377, 425, 276, 210, 800, 420, 350, 360, 538, 1100, 
1205, 314, 237, 610, 360, 540, 1038, 424, 310, 300, 444, 301, 268, 620, 
215, 652, 900, 525, 246, 360, 529, 500, 720, 270, 430, 671, 1770)