View Compilation Error

0_0_20814303_21549.cpp: In function 'void add(int)':
0_0_20814303_21549.cpp:14:8: error: 'j' was not declared in this scope
   f[n][j++]=k%10000;
        ^
0_0_20814303_21549.cpp: In function 'int main()':
0_0_20814303_21549.cpp:34:24: error: 'j' was not declared in this scope
       printf("%d",f[n][j]);
                        ^