#include<bits/stdc++.h>
#define f for(int i = 0;i < 3;i++)
using namespace std;
struct node{
    int a1,a2;
    int sum;
}a[3];
int main(){
    int n;
    cin >> n;
    f{
        cin >> a[i].a1 >> a[i].a2;
        int tmp = a[i].a1,j = 1;
        while(tmp < n)
            tmp += a[i].a1,j++;
        a[i].sum = j * a[i].a2;
    }
    f{
        if((a[i].sum) < min) min = a[i].sum;
    }
    cout << min;
    return 0;
}

各位大佬看看我这个蒟蒻为什么过不了编译T_T 编译信息：

main.cc: In function ‘int main()’:
main.cc:19:23: error: invalid operands of types ‘int’ and ‘<unresolved overloaded function type>’ to binary ‘operator<’
         if((a[i].sum) < min) min = a[i].sum;
            ~~~~~~~~~~~^~~~~
main.cc:19:41: error: overloaded function with no contextual type information
         if((a[i].sum) < min) min = a[i].sum;
                                         ^~~
main.cc:21:10: error: no match for ‘operator<<’ (operand types are ‘std::ostream {aka std::basic_ostream<char>}’ and ‘<unresolved overloaded function type>’)
     cout << min;
     ~~~~~^~~~~~
In file included from /usr/include/c++/7/istream:39:0,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from main.cc:1:
/usr/include/c++/7/ostream:108:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type& (*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]