1 files changed, 19 insertions, 0 deletions
diff --git a/cses/IntroductoryProblems/MissingNumber/main.cpp b/cses/IntroductoryProblems/MissingNumber/main.cpp
new file mode 100644
index 0000000..77f0f06
--- /dev/null
+++ b/cses/IntroductoryProblems/MissingNumber/main.cpp
@@ -0,0 +1,19 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+
+int main () {
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+  int n;
+  cin >> n;
+  long long sum = 0;
+  for (int i = 0; i < n - 1; i++) {
+    int x;
+    cin >> x;
+    sum += x;
+  }
+  long long x = n + 1;
+  long long ans = ((n * x) / 2) - sum;
+  cout << ans << endl;
+}