[20251212] BOJ / G5 / 떡파이어 / 권혁준

khj20006/202512/12 BOJ G5 떡파이어.md

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+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+using ll = long long;
+
+const ll MOD = 1e9 + 7;
+
+ll power(ll b) {
+    if(b == 0) return 1;
+    if(b == 1) return 2;
+    ll h = power(b>>1) % MOD;
+    h = (h*h)%MOD;
+    return (b&1) ? h * 2 % MOD : h;
+}
+
+int main(){
+    cin.tie(0)->sync_with_stdio(0);
+
+    ll N;
+    cin>>N;
+    cout<<(N == 0 ? 0 : power(N-1) % MOD);
+
+}
+```