一个关于程序运行错误的问题！

如图所示：

Run-Time Check Failure #3 - The variable 'MaxId' is being used without being initialized.

每当输入以下数据时，就会出现这个错误！

5 100 100 134 0 100

我的程序代码：

#include<iostream>
#include<cstdio>
using namespace std;
void get(int& X)
{
    X = 0;
    int w = 0; char ch = 0;
    while (!isdigit(ch)) { w |= ch == '-'; ch = getchar(); }
    while (isdigit(ch))X = (X << 3) + (X << 1) + (ch ^ 48), ch = getchar();
    if (w) X = -X;
}
int getbig(int a[], int n) {
    int Max = -0xbfbfbf;
    for (int i = 1; i <= n; i++) {
        if (a[i] >= Max)Max = a[i];
    }
    return Max;
}
int getbigId(int a[], int n) {
    int Max = -0xbfbfbf;
    int MaxId;
    for (int i = 1; i <= n; i++) {
        if (a[i] >= Max)Max = a[i], MaxId = i;
    }
    return MaxId;
}
int n, a[20005];
bool b[20005];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int ans = 0;
    get(n);
    for (int i = 1; i <= n; i++) {
        get(a[i]);
    }
    while (n) {
        ans += getbig(a, n);
        a[getbigId(a, n)] = 0;
        a[getbigId(a, n)] = 0;
        n -= 2;
    }
    cout << ans;
    return 0;
}