done

programs/p413/main.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+int main(void) {
+    int n;
+    int sum = 0;
+
+numInput:
+    printf("Input integer: ");
+    scanf("%d", &n);
+
+    if (n < 1) {
+        puts("Error: Please type in non-zero positive integer.");
+        goto numInput;
+    }
+
+    for (int i = 1; i <= n; i++) {
+        sum += i;
+    }
+
+    printf("ANS: %d", sum);
+
+    return 0;
+}