diff --git a/src/main.c b/src/main.c
index ac78f61..35471c6 100644
--- a/src/main.c
+++ b/src/main.c
@@ -12,10 +12,20 @@ int main(void) {
 	printf("Enter \"min, max\": ");
 	scanf("%lf, %lf", &a, &b);
 
+	if(a > b) {
+		fprintf(stderr, "`min' cannot be larger than `max'.\n");
+		return 1;
+	}
+
 	unsigned int parts;
 	printf("Number of parts: ");
 	scanf("%u", &parts);
 
+	if(parts == 0) {
+		fprintf(stderr, "`parts' must at least be 1.\n");
+		return 1;
+	}
+
 	double lRect, rRect, mRect, trap, simp;
 	lRect = rRect = mRect = trap = simp = 0;
 	for(unsigned int i = 0; i < parts; ++i) {