/in/foo.cc: In function 'int return_num(char*)':
/in/foo.cc:8:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0;i<strlen(s);i++)
               ~^~~~~~~~~~
/in/foo.cc: In function 'int return_num2(char*)':
/in/foo.cc:18:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=1;i<strlen(s);i++)
               ~^~~~~~~~~~
/in/foo.cc: In function 'int main(int, char**, char**)':
/in/foo.cc:33:16: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'char (*)[100000]' [-Wformat=]
   scanf("%s",&s);
                ^
/in/foo.cc:40:17: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'char (*)[100000]' [-Wformat=]
    scanf("%s",&s);
                 ^