solved 15717

Author: atobaum

15000/15717/15717.cpp

@@ -0,0 +1,31 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+
+ll n;
+int mod = 1000000007;
+
+int main() {
+  ios::sync_with_stdio(false); cin.tie(NULL);
+  cin>>n;
+  --n;
+
+  ll ans = 1, cur = 2;
+  if(n == 0){
+    ans = 1;
+  } 
+
+  while(n > 0){
+    if(n % 2) {
+      ans = (ans*cur) % mod;
+      n--;
+    }else {
+      n /= 2;
+      cur = (cur*cur) % mod;
+    }
+  }
+
+  cout<<ans<<"\n";
+  return 0;
+}