View Compilation Error

0_0_26704172_2776.cpp: In function 'int main()':
0_0_26704172_2776.cpp:26:19: error: 'c' was not declared in this scope
             check[c-'a'+1]=d-'a'+1;//打下一个转换表
                   ^
0_0_26704172_2776.cpp:26:28: error: 'd' was not declared in this scope
             check[c-'a'+1]=d-'a'+1;//打下一个转换表
                            ^