diff --git a/crystal/crystal.cpp b/crystal/crystal.cpp
index 934fc02..69c0c09 100644
--- a/crystal/crystal.cpp
+++ b/crystal/crystal.cpp
@@ -4,7 +4,7 @@ int n;
 long long m;
 long long a[500005];
 long long qsum[500005];
-bool checkb(int mid, int now, int tot) {
+bool checkb(int mid, long long now, int tot) {
     return mid * now - (qsum[tot] - qsum[tot - mid]) <= m;
 }
 long long check(long long now, int tot) {