diff --git a/source/_posts/answer4.md b/source/_posts/answer4.md
index 19e69fc..5aacbc4 100644
--- a/source/_posts/answer4.md
+++ b/source/_posts/answer4.md
@@ -14,42 +14,42 @@ tags:
 
 int main()
 {
-	// 输入
-	printf("最大公约数与最小公倍数计算");
-	int m, n;
-	printf("请输入正整数m和n：\nm = ");
-	if (scanf("%d", &m) != 1 || m <= 0) {
-		fprintf(stderr, "非法输入！\n");
-		exit(EXIT_FAILURE);
-	}
-	printf("n = ");
-	if (scanf("%d", &n) != 1 || n <= 0) {
-		fprintf(stderr, "非法输入！\n");
-		exit(EXIT_FAILURE);
-	}
+    // 输入        
+    printf("最大公约数与最小公倍数计算");
+    int m, n;
+    printf("请输入正整数m和n：\nm = ");
+    if (scanf("%d", &m) != 1 || m <= 0) {
+        fprintf(stderr, "非法输入！\n");
+        exit(EXIT_FAILURE);
+    }
+    printf("n = ");
+    if (scanf("%d", &n) != 1 || n <= 0) {
+        fprintf(stderr, "非法输入！\n");
+        exit(EXIT_FAILURE);
+    }
 
-	// a为较大者，b为较小者
-	int a, b;
-	if (m > n) {
-		a = m;
-		b = n;
-	} else {
-		a = n;
-		b = m;
-	}
+    // a为较大者，b为较小者
+    int a, b;
+    if (m > n) {
+        a = m;
+        b = n;
+    } else {
+        a = n;
+        b = m;
+    }
 
-	// 求最大公因数
-	int t = 1;
-	while (t != 0) {
-		t = a % b;
-		a = b;
-		b = t;
-	}
+    // 求最大公因数
+    int t = 1;
+    while (t != 0) {
+        t = a % b;
+        a = b;
+        b = t;
+    }
 
-	// 最小公倍数
-	int lcm = m * n / a;
+    // 最小公倍数
+    int lcm = m * n / a;
 
-	printf("最大公因数：%d\n最小公倍数：%d\n", a, lcm);
+    printf("最大公因数：%d\n最小公倍数：%d\n", a, lcm);
     return 0;
 }
 ```
@@ -71,20 +71,20 @@ $$
 
 int main()
 {
-	int a, n;
-	printf("P137-5\na = ");
-	scanf("%d", &a);
-	printf("n = ");
-	scanf("%d", &n);
+    int a, n;
+    printf("P137-5\na = ");
+    scanf("%d", &a);
+    printf("n = ");
+    scanf("%d", &n);
 
-	int sum = a;
+    int sum = a;
 
-	for (int i = 2; i <= n; ++i) {
-		sum *= 10;
-		sum += a * i;
-	}
-	printf("S = %d\n", sum);
-	return 0;
+    for (int i = 2; i <= n; ++i) {
+        sum *= 10;
+        sum += a * i;
+    }
+    printf("S = %d\n", sum);
+    return 0;
 }
 ```
 
@@ -133,13 +133,13 @@ $$
 
 int main()
 {
-	double t = 1e-6;
-	double x = 1.5;
-	while(fabs(2 * pow(x, 3) - 4 * pow(x, 2) + 3 * x - 6) >= t) {
-		x = (4 * pow(x, 3) - 4 * pow(x, 2) + 6) / (6 * pow(x, 2) - 8 * x + 3);
-	}
-	printf("P138-14\nx = %.3f\n", x);
-	return 0;
+    double t = 1e-6;
+    double x = 1.5;
+    while(fabs(2 * pow(x, 3) - 4 * pow(x, 2) + 3 * x - 6) >= t) {
+        x = (4 * pow(x, 3) - 4 * pow(x, 2) + 6) / (6 * pow(x, 2) - 8 * x + 3);
+    }
+    printf("P138-14\nx = %.3f\n", x);
+    return 0;
 }
 ```
 
@@ -151,25 +151,22 @@ int main()
 
 int main()
 {
-	double a = -10, b = 10, c = 0;
-	double t = 1e-6;
-	double fa = 2 * pow(a, 3) - 4 * pow(a, 2) + 3 * a - 6;
-	double fc = 2 * pow(c, 3) - 4 * pow(c, 2) + 3 * c - 6;
-	while (fabs(2 * pow(c, 3) - 4 * pow(c, 2) + 3 * c - 6) >= t) {
-		if (fabs(fc) < t) {
-			break;
-		}
-		if (fa * fc < 0) {
-			b = c;
-		} else {
-			a = c;
-			fa = fc;
-		}
-		c = (a + b) / 2;
-		fc = 2 * pow(c, 3) - 4 * pow(c, 2) + 3 * c - 6;
-	}
-	printf("P138-15\nx = %.3f\n", c);
-	return 0;
+    double a = -10, b = 10, c = 0;
+    double t = 1e-6;
+    double fa = 2 * pow(a, 3) - 4 * pow(a, 2) + 3 * a - 6;
+    double fc = 2 * pow(c, 3) - 4 * pow(c, 2) + 3 * c - 6;
+    while (fabs(2 * pow(c, 3) - 4 * pow(c, 2) + 3 * c - 6) >= t) {
+        if (fa * fc < 0) {
+            b = c;
+        } else {
+            a = c;
+            fa = fc;
+        }
+        c = (a + b) / 2;
+        fc = 2 * pow(c, 3) - 4 * pow(c, 2) + 3 * c - 6;
+    }
+    printf("P138-15\nx = %.3f\n", c);
+    return 0;
 }
 ```
 
@@ -183,28 +180,28 @@ int main()
 
 int main()
 {
-	printf("请输入%d个数字，用空格分隔：\n", LEN);
-	int a[LEN];
-	for (int i = 0; i < LEN; ++i) {
-		scanf("%d", a + i);
-	}
-	for (int i = 0; i < LEN - 1; ++i) {
-		int m = i;
-		for (int j = i + 1; j < LEN; ++j) {
-			if (a[j] < a[m]) {
-				m = j;
-			}
-		}
-		if (m != i) {
-			int tmp = a[i];
-			a[i] = a[m];
-			a[m] = tmp;
-		}
-	}
-	for (int i = 0; i < LEN; ++i) {
-		printf("%d ", a[i]);
-	}
-	printf("\n");
-	return 0;
+    printf("请输入%d个数字，用空格分隔：\n", LEN);
+    int a[LEN];
+    for (int i = 0; i < LEN; ++i) {
+        scanf("%d", a + i);
+    }
+    for (int i = 0; i < LEN - 1; ++i) {
+        int m = i;
+        for (int j = i + 1; j < LEN; ++j) {
+            if (a[j] < a[m]) {
+                m = j;
+            }
+        }
+        if (m != i) {
+            int tmp = a[i];
+            a[i] = a[m];
+            a[m] = tmp;
+        }
+    }
+    for (int i = 0; i < LEN; ++i) {
+        printf("%d ", a[i]);
+    }
+    printf("\n");
+    return 0;
 }
 ```