C program in Linux environment

The below program giving wrong output when negative integer entered at command line for two consecutive times . can we correct that? #include <stdio.h> #include <unistd.h> int main() { int number = 0, status; pid_t pid; printf("Please enter a number n"); scanf("%d", &number); if(number<0) { printf("Please enter a positive number, greather than 0 n"); scanf("%d", &number); } pid = fork(); if(pid < 0) { printf(" Unsuccessful to create Child Process n"); return 0; } else if(pid == 0) { printf("%d ",number); do { if(number%2 != 0) { number = (number*3)+1; } else if(number%2 == 0) { number = number/2; } printf("%d ",number); }while(number != 1); } else { printf("\npid %d ",pid); wait(&status); } return 0; }