foo.cpp:13:32: warning: trigraph ??- ignored, use -trigraphs to enable [-Wtrigraphs]
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
 ^
foo.cpp: In function 'int f(int, int)':
foo.cpp:13:18: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                  ^
foo.cpp:13:19: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                   ^
foo.cpp:13:20: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                    ^
foo.cpp:13:21: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                     ^
foo.cpp:13:22: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                      ^
foo.cpp:13:23: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                       ^
foo.cpp:13:24: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                        ^
foo.cpp:13:25: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                         ^
foo.cpp:13:26: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                          ^
foo.cpp:13:29: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                             ^
foo.cpp:13:30: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                              ^
foo.cpp:13:31: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                               ^
foo.cpp:13:32: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                ^
foo.cpp:13:33: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                 ^
foo.cpp:13:49: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                 ^
foo.cpp:13:50: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                  ^
foo.cpp:13:51: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                   ^
foo.cpp:13:52: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                    ^
foo.cpp:13:53: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                     ^
foo.cpp:13:54: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                      ^
foo.cpp:13:55: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;
                                                       ^
foo.cpp:13:56: error: expected primary-expression before '?' token
  return f(n-k,k)/?????????1??????-1/+f(n-1,k-1)/????????????1???k-1?/;