ll modpow(ll a, ll b) { ll ans = 1, base = a%MOD; while(b != 0) { if(b&1 != 0) ans = (ans*base)%MOD; base = (base*base)%MOD; b >>= 1; } return ans%MOD; }
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原文：https://www.cnblogs.com/lishengkangshidatiancai/p/10360292.html
