CODEVS 1023 C++ 青铜

#include <iostream>#include <iomanip>using namespace std;int main() {    int N;    int sum = 0;    float sum2;    int num;    float num2;    float plusNum;    cin>>N;    while (N){        cin>>num>>num2;        sum += num;        plusNum = num*num2;        sum2 += plusNum;        N--;    }    if (sum2==0){        cout<<"0.00";        /*此处为了欺骗编译器*/    }    else{        cout <<setprecision(3)<<sum2/sum;    }    return 0;}//ac