View Compilation Error

0_0_33875152_15150.cpp: In function 'int main()':
0_0_33875152_15150.cpp:7:2: error: expected initializer before 'int'
  int sum=0,cost;                 //sum:测试用例数量，cost:总共花费的钱  
  ^
0_0_33875152_15150.cpp:8:7: error: 'N' was not declared in this scope
  cin>>N;
       ^
0_0_33875152_15150.cpp:11:3: error: 'sum' was not declared in this scope
   sum++;                      //控制最后输出结果的序号 
   ^
0_0_33875152_15150.cpp:17:3: error: 'cost' was not declared in this scope
   cost=n*b+2*a;               //记录必定花费的钱,即此处未加上用于比较的中间几天的往返钱或工资 
   ^