diff --git a/6.0s1.h b/6.0s1.h
new file mode 100644
index 0000000..fe1ff54
--- /dev/null
+++ b/6.0s1.h
@@ -0,0 +1,109 @@
+#ifndef S1_6_0_H
+#define S1_6_0_H
+
+struct s1_location {
+    const char *file;
+    int line;
+};
+
+typedef int       S1_INT;
+typedef long long S1_LONG;
+typedef double    S1_DOUBLE;
+typedef char      S1_CHAR;
+
+
+#define S1_LOC() (struct s1_location){__FILE__, __LINE__}
+
+#   ifndef S1_6_0_H_IMPL
+
+#   include <stdio.h>
+#   include <stdlib.h>
+
+// 1. assert 
+void s1_assert(int value, const char *reason, struct s1_location loc) {
+    if (!value) {
+        fprintf(stderr, "%s:%d %s\n", loc.file, loc.line, reason);
+        exit(3);
+    }
+}
+
+
+// 2. simple IO
+
+void write_int(S1_INT value, struct s1_location loc) {
+    int rc = printf("%d", value);
+    s1_assert(rc != EOF, "Error: write_int", loc);
+}
+
+void write_long(S1_LONG value, struct s1_location loc) {
+    int rc = printf("%lld", value);
+    s1_assert(rc != EOF, "Error: write_long", loc);
+}
+
+void write_double(S1_DOUBLE value, struct s1_location loc) {
+    int rc = printf("%f", value);
+    s1_assert(rc != EOF, "Error: write_long", loc);
+}
+
+void write_char(S1_CHAR value, struct s1_location loc) {
+    int rc = printf("%c", value);
+    s1_assert(rc != EOF, "Error: write_char", loc);
+}
+
+#define write_int(value)      write_int(value, S1_LOC())
+#define write_long(value)     write_long(value, S1_LOC())
+#define write_double(value)   write_double(value, S1_LOC())
+#define write_char(value)     write_char(value, S1_LOC())
+
+S1_INT read_int(struct s1_location loc) {
+    S1_INT value = 0;
+    int rc = scanf("%d", &value);
+    s1_assert(rc == 1, "Error: read_int", loc);
+    return value;
+}
+
+S1_LONG read_long(struct s1_location loc) {
+    S1_LONG value = 0;
+    int rc = scanf("%lld", &value);
+    s1_assert(rc == 1, "Error: read_long", loc);
+    return value;
+}
+
+S1_DOUBLE read_double(struct s1_location loc) {
+    S1_DOUBLE value = 0.0;
+    int rc = scanf("%lf", &value);
+    s1_assert(rc == 1, "Error: read_double", loc);
+    return value;
+}
+
+S1_CHAR read_char(struct s1_location loc) {
+    S1_CHAR value = 0;
+    int rc = scanf("%c", &value);
+    s1_assert(rc == 1, "Error: read_char", loc);
+    return value;
+}
+
+void read_pnl(struct s1_location loc) {
+    S1_CHAR value = 0;
+    while (1) {
+        int rc = scanf("%c", &value);
+        if (feof(stdin)) {
+            break;
+        }
+        s1_assert(rc == 1, "Error: read_pnl", loc);
+        if (value == '\n') {
+            break;
+        }
+    }
+}
+
+
+#define read_int()      read_int(S1_LOC())
+#define read_long()     read_long(S1_LOC())
+#define read_double()   read_double(S1_LOC())
+#define read_char()     read_char(S1_LOC())
+#define read_pnl()      read_pnl(S1_LOC())
+#   endif
+
+
+#endif
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