added programs

programs/prog4/main.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+int main(void) {
+    int n1;
+    int n2;
+    int n3;
+
+    printf("Input three integers.\n");
+    printf("Integer n1: ");
+    scanf("%d", &n1);
+    printf("Integer n2: ");
+    scanf("%d", &n2);
+    printf("Integer n3: ");
+    scanf("%d", &n3);
+
+    printf("The sum of three integers is %d.", n1 + n2 + n3);
+
+    return 0;
+}