View Compilation Error

0_0_19570028_30078.cpp: In function 'int main()':
0_0_19570028_30078.cpp:4:25: error: 'n' was not declared in this scope
  while(~scanf("%d%d%d",&n,&st,&ed))
                         ^
0_0_19570028_30078.cpp:4:28: error: 'st' was not declared in this scope
  while(~scanf("%d%d%d",&n,&st,&ed))
                            ^
0_0_19570028_30078.cpp:4:32: error: 'ed' was not declared in this scope
  while(~scanf("%d%d%d",&n,&st,&ed))
                                ^
0_0_19570028_30078.cpp:6:11: error: 'ans' was not declared in this scope
   if(n==1)ans=0;//只有一根柱子
           ^
0_0_19570028_30078.cpp:7:18: error: 'ans' was not declared in this scope
   else if(st==ed)ans=-1;//无法再返回了
                  ^
0_0_19570028_30078.cpp:11:4: error: 'ans' was not declared in this scope
    ans=0;
    ^
0_0_19570028_30078.cpp:27:17: error: 'ans' was not declared in this scope
   printf("%d\n",ans);
                 ^