diff --git a/mystr_idx b/mystr_idx
new file mode 100755
index 0000000..cdfd65f
Binary files /dev/null and b/mystr_idx differ
diff --git a/mystr_idx.c b/mystr_idx.c
new file mode 100644
index 0000000..a3f33d2
--- /dev/null
+++ b/mystr_idx.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <string.h>
+int mystr_idx(char *str, char *substr);
+int main(int argc, char **argv)
+{
+	printf("Print you string\n");
+	char s[100]; scanf("%s", s);
+	printf("Print substring\n");
+	char ss[100]; scanf("%s", ss);
+	printf("Your substr has intex:%d\n", mystr_idx(s, ss));
+	return 0;
+}
+int mystr_idx(char *str, char *substr)
+{	
+		int indx = strstr(str, substr) - str;
+		if(strstr(str, substr) == NULL)
+		{indx = -1;}
+		
+		return indx;
+}