James is running around a square field. He starts at point A, then runs around the perimeter, passing through points B, C, and D, until he gets back to point A. Then he cuts across the diagonal to point C. In total, he covers 271 m. If AB¯¯¯¯¯¯¯¯
A
B
¯
is 50 m long, what is the length of the diagonal AC¯¯¯¯¯¯¯¯
A
C
¯
?