View Compilation Error

0_0_37864234_19892.cpp: In function 'll powmod(ll, ll)':
0_0_37864234_19892.cpp:10:45: error: expected ';' before 'ssert'
 ll powmod(ll a,ll b) {ll res=1;a%=mod; a    ssert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
                                             ^