# 기본 수학 1: 1단계 (손익분기점)

import sys

a, b, c = sys.stdin.readline().rstrip().split()
if int(c) - int(b) < 1: print(-1)
else: print(int(int(a) / (int(c) - int(b)) + 1))
084c3de466de17ae9f719a2a8065be3b5ff8eb5b
<mask token>

<mask token>
if int(c) - int(b) < 1:
    print(-1)
else:
    print(int(int(a) / (int(c) - int(b)) + 1))

<mask token>
a, b, c = sys.stdin.readline().rstrip().split()
if int(c) - int(b) < 1:
    print(-1)
else:
    print(int(int(a) / (int(c) - int(b)) + 1))

import sys
a, b, c = sys.stdin.readline().rstrip().split()
if int(c) - int(b) < 1:
    print(-1)
else:
    print(int(int(a) / (int(c) - int(b)) + 1))

# 기본 수학 1: 1단계 (손익분기점)

import sys

a, b, c = sys.stdin.readline().rstrip().split()
if int(c) - int(b) < 1: print(-1)
else: print(int(int(a) / (int(c) - int(b)) + 1))