diff --git a/daima/c.txt b/daima/c.txt
new file mode 100644
index 0000000..8d43f0c
--- /dev/null
+++ b/daima/c.txt
@@ -0,0 +1,46 @@
+#include <iostream>
+
+using namespace std;
+const double e = 2.718281828459;
+
+double log(double x)
+{
+	long t = 0;
+	while (x > 1)
+	{
+		x /= e;
+		++t;
+	}
+	x = x - 1;
+	double ret = 0;
+	int k = 1;
+	double temp;
+	double c = 1;
+	double xx = 1;
+	while (1)
+	{
+		xx *= x;
+		temp = c * xx / k;
+		c *= -1;
+		ret += temp;
+		++k;
+		if (temp > -0.00000001)
+			break;
+	}
+	return ret + t;
+}
+
+int main()
+{
+	double a, x;				// 计算log(a,x);
+	// 用ln(x)/ln(a)计算。
+	
+		cin >> a >> x;
+		if (a <= 0 || x <= 0 || a == 1)
+		{
+			cout << "输入不正确！" << endl;
+		}
+		double ans = log(x) / log(a);
+		cout << ans << endl;	// log(x)返回x的自然对数，使用虚include"cmath"或"math.h"。
+	return 0;
+}