View Compilation Error

0_0_28750725_20712.cpp:10:7: error: 'N' was not declared in this scope
 int a[N], b[N];   // a 为数列， b 保存 a[0...i] 能构造出的最大的数
       ^
0_0_28750725_20712.cpp:10:13: error: 'N' was not declared in this scope
 int a[N], b[N];   // a 为数列， b 保存 a[0...i] 能构造出的最大的数
             ^
0_0_28750725_20712.cpp: In function 'int main()':
0_0_28750725_20712.cpp:18:9: error: 'a' was not declared in this scope
         a[0] = b[0] = 1;
         ^
0_0_28750725_20712.cpp:18:16: error: 'b' was not declared in this scope
         a[0] = b[0] = 1;
                ^