main()
{
char input[80];
int num, half;
int factor;
int prime;
while (fgets(input,sizeof(input)-1, stdin) != NULL) {
num = atoi (input);
do {
half = num/2;
for (prime=1, factor=2; factor < half && prime; factor++)
if ( num % factor == 0 ) prime = 0;
if (prime) {
printf ("%d is a prime number\n", num);
}
else {
num++;}
} while (!prime);
}
}
