java - Print Fibonacci number -

my program supposed output fibonacci number based on user has entered (ex. if enter 7 program output 13). portion works. part having trouble when program checks makes sure number user entered positive , less or equal 70. it supposed ask user input again, instead outputs "fibonacci #-1 0" , stops. here's code:

import java.util.scanner;  public class scalvert_fibonacci { public static void main ( string args[] )  {     scanner input = new scanner ( system.in );      int sum = 0;     int num;     int f1 = 0, f2 = 0, f3 = 1;      system.out.print("which fibonacci number like? ");     num = input.nextint();       if (num == 0)     return 0;      else if (num == 1)     return 1;      while (num < 0 || num > 70)     {         system.out.print("which fibonacci number like? ");         num = input.nextint();      }          for(int = 1; <= num; i++)         {                 f1 = f2;                 f2 = f3;                 f3 = f1 + f2;         }         system.out.printf("fibonacci #%d %d\n",num, f2); } } 

using might solve problem

if(num<0 || num>70) {     //ask number again } else {     //calculate }  or use  if( 0 < num < 71 ) {     //calculate } else {      //ask valid number }