/in/foo.cc: In function 'int main()':
/in/foo.cc:18:24: error: 'pow' was not declared in this scope
   18 |    a1 += (s[i] - 48) * pow(10,x);
      |                        ^~~
/in/foo.cc:25:24: error: 'pow' was not declared in this scope
   25 |    a2 += (s[i] - 48) * pow(10, x);
      |                        ^~~
/in/foo.cc:32:24: error: 'pow' was not declared in this scope
   32 |    a3 += (s[i] - 48) * pow(10, x);
      |                        ^~~
/in/foo.cc:39:24: error: 'pow' was not declared in this scope
   39 |    a4 += (s[i] - 48) * pow(10, x);
      |                        ^~~