diff --git a/5_practice.c b/5_practice.c
index 70d6651..622ce8f 100644
--- a/5_practice.c
+++ b/5_practice.c
@@ -9,18 +9,36 @@ int main() {
 	time_t t;
 
 	// Input the number N
-	
-	
+	printf("Input the number N:\n");
+	scanf("%d",&N);
+
 	// Locate the memory for x, yr, yi;
+	x = (double *)malloc(N * sizeof(double));
+	yr = (double *)malloc(N * sizeof(double)); 
+	yi = (double *)malloc(N * sizeof(double));
 
 	// Initial setting for x, for example, x[k] = k
+	for ( k = 0; k < N; k++)
+	{
+		x[k] = k;
+		yr[k] = 0;
+		yi[k] = 0;
+	}
 	
 	
 	
 	
 	t = clock();	
 	// yr[n]+i*yi[n] = sum(exp(-i 2 Pi k n / N)*x[k], k=0..N-1), n=0..N-1 
-
+	for ( n = 0; n < N; n++)
+	{
+		for ( k = 0; k < N; k++)
+		{
+			yr[n] += cos(2 * M_PI * k * n / N ) * x[k];
+			yi[n] -= sin(2 * M_PI * k * n / N ) * x[k];
+		}
+	}
+	
 
 
 
@@ -32,8 +50,9 @@ int main() {
 	printf("%d ms for discrete Fourier Transform of %d elements\n", t, N);
 
 	// free the memory located by x, yr, yi
-	
-	
+	free(x);
+	free(yr);
+	free(yi);	
 	
 	return 100;
 }