What is the string that will unlock phase three of binary bomb lab?

Dump of assembler code for function phase_3:

my input was 6 714

=> 0x0000000000400f4b <+0>: sub $0x18,%rsp

0x0000000000400f4f <+4>: lea 0x8(%rsp),%rcx

0x0000000000400f54 <+9>: lea 0xc(%rsp),%rdx

0x0000000000400f59 <+14>: mov $0x4027ed,%esi

0x0000000000400f5e <+19>: mov $0x0,%eax

0x0000000000400f63 <+24>: callq 0x400c10 <__isoc99_sscanf@plt>

0x0000000000400f68 <+29>: cmp $0x1,%eax

0x0000000000400f6b <+32>: jg 0x400f72

0x0000000000400f6d <+34>: callq 0x401574

0x0000000000400f72 <+39>: cmpl $0x7,0xc(%rsp)

0x0000000000400f77 <+44>: ja 0x400fdf

0x0000000000400f79 <+46>: mov 0xc(%rsp),%eax

0x0000000000400f7d <+50>: jmpq *0x402520(,%rax,8)

0x0000000000400f84 <+57>: mov $0x0,%eax

0x0000000000400f89 <+62>: jmp 0x400f90

0x0000000000400f8b <+64>: mov $0x69,%eax

0x0000000000400f90 <+69>: sub $0x2a8,%eax

0x0000000000400f95 <+74>: jmp 0x400f9c

0x0000000000400f97 <+76>: mov $0x0,%eax

0x0000000000400f9c <+81>: add $0x23d,%eax

0x0000000000400fa1 <+86>: jmp 0x400fa8

0x0000000000400fa3 <+88>: mov $0x0,%eax