/in/foo.cc: In function 'int pow(int, int, int)':
/in/foo.cc:9:10: warning: statement has no effect [-Wunused-value]
     for(b; b; b>>=1)
          ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:22:41: warning: format '%lld' expects argument of type 'long long int', but argument 2 has type 'int' [-Wformat=]
     printf("a^b mod p=%lld\n",pow(a,b,p));
                                         ^