/in/foo.cc: In function 'bool check()':
/in/foo.cc:7:14: error: 'x' was not declared in this scope
 { while(cin>>x>>y)
              ^
/in/foo.cc:7:17: error: 'y' was not declared in this scope
 { while(cin>>x>>y)
                 ^
/in/foo.cc:11:16: error: 'b' was not declared in this scope
         memset(b,0,sizeof b);
                ^
/in/foo.cc:12:16: error: 'c' was not declared in this scope
         memset(c,0,sizeof c);
                ^
/in/foo.cc:14:19: error: 'len2' was not declared in this scope
         for(int i=len2-1,j=0; i>=0; i--,j++) b[j]=y[i]-'0';
                   ^~~~
/in/foo.cc:14:41: error: 'j' was not declared in this scope
         for(int i=len2-1,j=0; i>=0; i--,j++) b[j]=y[i]-'0';
                                         ^
/in/foo.cc:16:28: error: 'len2' was not declared in this scope
             for(int j=0; j<len2; j++)//模拟乘法将两个数的每一位均和对方相乘，存入对应的结果中。
                            ^~~~
/in/foo.cc:19:22: error: 'maxn' was not declared in this scope
         for(i=0; i<2*maxn; i++)//处理进位问题
                      ^~~~
/in/foo.cc:30:1: error: a function-definition is not allowed here before '{' token
 {
 ^
/in/foo.cc:50:1: error: expected '}' at end of input
 }
 ^
/in/foo.cc:50:1: error: expected '}' at end of input
/in/foo.cc:50:1: warning: no return statement in function returning non-void [-Wreturn-type]