Add problem 4 solution

include/p4.h

@@ -0,0 +1,7 @@
+#ifndef P4_H
+#define P4_H
+
+int prompt_value(void);
+
+#endif
+

src/main.c

@@ -3,6 +3,7 @@
 #include "p1.h"
 #include "p2.h"
 #include "p3.h"
+#include "p4.h"
 #include "p5.h"
 
 void print_int_arr(int* arr, int size) {
@@ -44,7 +45,12 @@ int main(void) {
 	double sum_of_file = sum_file("input_p3.dat");
 
 	printf("Sum of file: %.2lf\n", sum_of_file);
-	//
+
+	// Problem 4
+	printf("Problem 4:\n");
+	int p4_value = prompt_value();
+	printf("You entered: %d\n", p4_value);
+
 	// Problem 5
 	printf("Problem 5:\n");
 	int num_alphanum = count_alphanumeric("Hello World!!");

src/p4.c

@@ -0,0 +1,17 @@
+#include "p4.h"
+
+#define _CRT_SECURE_NO_WARNINGS
+
+#include <stdio.h>
+
+int prompt_value(void) {
+	int value = 0;
+
+	do {
+		printf("Please enter an integer between 1 and 100: ");
+		scanf("%d", &value);
+	} while (value < 1 || value > 100);
+
+	return value;
+}
+