diff --git a/.gitignore b/.gitignore
index 1e19735..b82e541 100644
--- a/.gitignore
+++ b/.gitignore
@@ -252,3 +252,6 @@ dkms.conf
 
 a.out
 *.swp
+a.exe
+*.in
+*.out
diff --git a/390/solutie.cpp b/390/solutie.cpp
new file mode 100644
index 0000000..17a7b14
--- /dev/null
+++ b/390/solutie.cpp
@@ -0,0 +1,18 @@
+#include <fstream>
+
+using namespace std;
+
+ifstream fin("planta.in");
+ofstream fout("planta.out");
+
+int main() {
+	int d,a,b,n,i;
+	fin >> d >> a >> b >> n;
+	int z = n / 2;
+	d = d + a * z - b * z;
+	if (n % 2 == 1) {
+		d = d + a;
+	}
+	fout << d;
+	return 0;
+}