View Compilation Error

0_0_27235305_6015.cpp: In function 'int Scan()':
0_0_27235305_6015.cpp:6:33: error: 'flag' was not declared in this scope
     if((ch = getchar()) == '-') flag = 1;  
                                 ^
0_0_27235305_6015.cpp:7:37: error: 'res' was not declared in this scope
     else if(ch >= '0' && ch <= '9') res = ch - '0';  
                                     ^
0_0_27235305_6015.cpp:9:9: error: 'res' was not declared in this scope
         res = res * 10 + (ch - '0');  
         ^
0_0_27235305_6015.cpp:10:12: error: 'flag' was not declared in this scope
     return flag ? -res : res;  
            ^
0_0_27235305_6015.cpp:10:20: error: 'res' was not declared in this scope
     return flag ? -res : res;  
                    ^