create dev channel

zeta/py/completed/1316.py

@@ -0,0 +1,19 @@
+N = int(input())
+c = 0
+for i in range(N):
+    s = input()
+    beforehead = s[0]
+    
+    befores = set()
+    befores.add(beforehead)
+    for t in s:
+        if t == beforehead:
+            continue
+        elif t in befores:
+            break
+        else:
+            beforehead = t
+            befores.add(t)
+    else:
+        c+=1
+print(c)