View Compilation Error

0_0_33672190_7262.cpp:6:1: error: expected initializer before 'const'
 const int MOD = 998244353;
 ^
0_0_33672190_7262.cpp:23:1: error: 'ld' does not name a type
 ld cal(int x,int y)//计算两条直线的交点
 ^
0_0_33672190_7262.cpp: In function 'int main()':
0_0_33672190_7262.cpp:58:43: error: 'cal' was not declared in this scope
    while(top >= 3 && cal(s[top-2],s[top-1]) < cal(s[top-1],i))
                                           ^