diff --git a/2025.05.09/12Ex/Makefile b/2025.05.09/12Ex/Makefile
index 590d992..ec51082 100644
--- a/2025.05.09/12Ex/Makefile
+++ b/2025.05.09/12Ex/Makefile
@@ -20,7 +20,7 @@ else
 	CLEAN = rm -f
 endif
 
-TARGET = a08.$(EXE)
+TARGET = a12.$(EXE)
 OBJ = main.o solve.o
 
 %.o: %.c
diff --git a/2025.05.09/12Ex/main.c b/2025.05.09/12Ex/main.c
index 5af4a17..58012bf 100644
--- a/2025.05.09/12Ex/main.c
+++ b/2025.05.09/12Ex/main.c
@@ -6,29 +6,30 @@
 #include "init_f.h"
 #include "solve.h"
 
-/* ./a08.out a b eps k */
+/* ./a12.out a b eps k_x k_y */
 int main (int argc, char *argv[])
 {
 	double t, integral, a, b, eps;
-	int k, n, calls, task = 8;
+	int x, y, n, calls, task = 12;
 	
 	double (*f_lst[]) (double) = {f0, f1, f2, f3, f4, f5, f6};
 	int len_f = sizeof(f_lst) / sizeof(f_lst[0]);
 
 	if (
-			!((argc == 5) && 
+			!((argc == 6) && 
 			sscanf(argv[1], "%lf", &a) == 1 &&
 			sscanf(argv[2], "%lf", &b) == 1 &&
 			((sscanf(argv[3], "%lf", &eps) == 1) && (eps > 0)) &&
-			((sscanf(argv[4], "%d", &k) == 1) && ((0 <= k) && (k < len_f))))
+			((sscanf(argv[4], "%d", &x) == 1) && ((0 <= x) && (x < len_f))) &&
+			((sscanf(argv[5], "%d", &y) == 1) && ((0 <= y) && (y < len_f))))
 	) {
-		fprintf(stderr, "Usage: %s a b eps k\n", argv[0]);
+		fprintf(stderr, "Usage: %s a b eps k_x k_y\n", argv[0]);
 		return -1;
 	}
 
 
 	t = clock();
-	n = t8_solve(f_lst[k], a, b, eps, &integral);
+	n = t12_solve(f_lst[x], f_lst[y], a, b, eps, &integral);
 	t = (clock() - t) / CLOCKS_PER_SEC;
 	
 	calls = get_call_count();
diff --git a/2025.05.09/12Ex/solve.c b/2025.05.09/12Ex/solve.c
index aeea51e..d75d2e3 100644
--- a/2025.05.09/12Ex/solve.c
+++ b/2025.05.09/12Ex/solve.c
@@ -5,42 +5,49 @@
 
 #define MAX_ITER 30
 
-int t8_solve (
-		double (*f) (double), 
+int t12_solve (
+		double (*xt) (double), 
+		double (*yt) (double),
 		double a, double b,
 		double eps, double *res
 ) {
 	int it;
 
-	double n = 1;
-	double h = (b - a);
-	double integ_n = (f(a) + f(b)) * h*0.5;
+	int n = 1;
+	double h = (b - a) * 0.5;
+	double x = xt(b) - xt(a);
+	double y = yt(b) - yt(a);
+	double len_n = sqrt(x * x + y * y);
 
 	for (it = 1; it <= MAX_ITER; ++it)
 	{
-		double x = a + h*0.5;
-		double integ_2n = 0;
+		double t = a;
+		double tn = a + h;
+		double len_2n = 0;
 	
 		for (int i = 0; i < n; i++)
 		{
-			integ_2n += f(x);
-			x += h;
+			x = xt(tn) - xt(t);
+			y = yt(tn) - yt(t);
+			len_2n += sqrt(x * x + y * y);
+
+			t = tn;
+			tn += h;
 		}
 
 		h *= 0.5;
-		integ_2n = integ_2n * h + integ_n * 0.5;
 
-		if (fabs(integ_2n - integ_n) < eps)
+		if (fabs(len_2n - len_n) < eps)
 			break;
 		
-		integ_n = integ_2n;
-		n *= 2;
+		len_n = len_2n;
+		n <<= 1;
 	}
 
 	if (it > MAX_ITER) 
 		return -1;
 	
-	*res = integ_n;
+	*res = len_n;
 
 	return n;
 }
diff --git a/2025.05.09/12Ex/solve.h b/2025.05.09/12Ex/solve.h
index 8a997b4..f5b3183 100644
--- a/2025.05.09/12Ex/solve.h
+++ b/2025.05.09/12Ex/solve.h
@@ -1,8 +1,9 @@
 #ifndef SOLVE_H
 #define SOLVE_H
 
-int t8_solve (
-		double (*f) (double), 
+int t12_solve (
+		double (*x) (double), 
+		double (*y) (double),
 		double a, double b,
 		double eps, double *res
 );