/in/foo.cc: In function 'int main()':
/in/foo.cc:18:25: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long long int' [-Wformat=]
  printf("%d\n",(x%b+b)%b);
                         ^
/in/foo.cc:17:6: warning: unused variable 'gcd' [-Wunused-variable]
  int gcd=exgcd(a,b,x,y);
      ^~~