atcoder/abc071B

Author: xirc

atcoder/abc071/B/main.cpp

@@ -0,0 +1,30 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    string S;
+    cin >> S;
+
+    vector<bool> used(26, false);
+    for (auto ch : S) {
+        int i = (ch - 'a');
+        used[i] = true;
+    }
+    int i;
+    for (i = 0; i < 26; ++i) {
+        if (used[i]) continue;
+        break;
+    }
+    if (i < 26) {
+        cout << char('a' + i) << endl;
+    } else {
+        cout << "None" << endl;
+    }
+
+    return 0;
+}