小号@ikunyyh

代码思路：首先找到规律，易有：

最后加个高精度，进位一下即可

#include <bits/stdc++.h>
using namespace std;
#define int long long

const int maxn = 1e7+7;
int N;
int a[maxn];
int ans[maxn];

inline void print (int *b) {
    for (register int i = b[0]; i >= 1; i--)
        cout << b[i];
    cout << endl;
    return;
}

inline void get (void) {
    ans[0] = N;
    for (register int i = 1; i <= ans[0]; i++) {
        ans[i + 1] += ans[i] / 10;
        ans[i] %= 10;
    }
    return;
}

signed main(signed argc, char const *argv[]) {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    char m;
    int k = 0;
    cin >> N;
    for (register int i = 1; i <= N; i++) {
        cin >> m;
        a[i] = m - 48;
    }
    int prefix = 0;
    for (register int i = 1; i <= N; i++) {
        prefix += i * a[i];
        ans[N-i+1] = prefix;
    }
    get();
    print(ans);
    return 0;
}