solved 24533

Author: atobaum

24000/24533/24533.cpp

@@ -0,0 +1,25 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+
+#define FOR(i, a, b) for (int i = a; i < b; i++)
+int N;
+ll a, b, c, d, ans=0;
+
+// energy generation satisfies commutivity and associativity
+int main() {
+  ios::sync_with_stdio(false); cin.tie(NULL);
+  cin>>N;
+  cin>>a>>b;
+  FOR(i, 1, N){
+    cin>>c>>d;
+    ans += a*d+b*c;
+    a+=c;
+    b+=d;
+  }
+
+  cout<<ans;
+
+  return 0;
+}