Create 1637C-AndrewAndStones.cpp

Author: DionysiosB

1637C-AndrewAndStones.cpp

@@ -0,0 +1,22 @@
+#include <cstdio>
+typedef long long ll;
+
+int main(){
+
+    long t; scanf("%ld", &t);
+    while(t--){
+        long n; scanf("%ld", &n);
+        bool ones(true), threeodd(false); ll cnt(0);
+        for(long p = 0; p < n; p++){
+            ll x; scanf("%lld", &x);
+            if(p == 0 || p == n - 1){continue;}
+            if(n == 3 && p == 1){threeodd = x % 2;}
+            if(x > 1){ones = false;}
+            cnt += (x + 1) / 2;
+        }
+
+        bool impossible = ones || threeodd;
+        printf("%lld\n", impossible ? (-1) : cnt);
+    }
+
+}