foo.cc:9:24: error: extended character − is not valid in an identifier
    9 |                 f[i]=f[i−1]*(4∗i−2)/(i+1);
      |                        ^
foo.cc:9:30: error: extended character ∗ is not valid in an identifier
    9 |                 f[i]=f[i−1]*(4∗i−2)/(i+1);
      |                              ^
foo.cc:9:30: error: extended character − is not valid in an identifier
foo.cc: In function ‘int main()’:
foo.cc:9:24: error: ‘i−1’ was not declared in this scope
    9 |                 f[i]=f[i−1]*(4∗i−2)/(i+1);
      |                        ^~~
foo.cc:9:30: error: unable to find numeric literal operator ‘operator""∗i−2’
    9 |                 f[i]=f[i−1]*(4∗i−2)/(i+1);
      |                              ^~~~~
foo.cc:9:30: note: use ‘-fext-numeric-literals’ to enable more built-in suffixes