upload

1/F.cpp

@@ -0,0 +1,34 @@
+#include <iostream>
+
+int main() {
+    int n;
+    std::cin >> n;
+
+    int *days = new int[n];
+    int *sums_lr = new int[n];
+    int *sums_rl = new int[n];
+
+    for (int i = 0; i < n; ++i) {
+        std::cin >> days[i];
+        sums_lr[i] = 0;
+        sums_rl[i] = 0;
+    }
+
+    for (int i = 1; i < n; ++i) {
+        sums_lr[i] = sums_lr[i-1] + days[i-1];
+    }
+
+    for (int i = n-2; i > -1; --i) {
+        sums_rl[i] = sums_rl[i+1] + days[i+1];
+    }
+
+    for (int i = 0; i < n; ++i) {
+        if (sums_rl[i] == sums_lr[i]) {
+            std::cout << i;
+            return 0;
+        }
+    }
+
+    std::cout << -1;
+    return 0;
+}