p1536.cpp

#include <iostream>

#define N 2000

void process(int n);

void set0(int k[N]);

void set1(int k[N]);

void copyarr(int from[N], int to[N]);

void mul(int arr[N], int k);

void add(int a[N], int b[N]);

void print(int a[N]);

using namespace std;

int main() {
    int n;
    while (true) {
        cin >> n;
        if (n == -1) break;
        process(n);
    }
    return 0;
}

void process(int n) {
    int f[N],fs[N],fprev[N],fsprev[N];
    set0(f); set1(fs);
    for (int i=2; i<=n; i++) {
        copyarr(f,fprev);
        copyarr(fs,fsprev);
        copyarr(fsprev,f);
        mul(f,i-1);
        copyarr(fprev,fs);
        add(fs,f);
    }
    print(f);
}

void print(int a[N]) {
    int i=N-1;
    while (a[i]==0 && i>=0) i--;
    if (i==-1) cout << 0; else { 
        while (i>=0) {
            cout << a[i--];
        }
    }
    cout << endl;
}

void add(int a[N], int b[N]) {
    int perenos = 0;
    for(int i=0; i<N; i++) {
        perenos += (a[i]+b[i]);
        a[i] = perenos % 10;
        perenos /= 10;
    }
}

void mul(int arr[N], int k) {
    int perenos = 0;
    for (int i=0; i<N; i++) {
        perenos = arr[i]*k+perenos;
        arr[i] = perenos % 10;
        perenos /= 10;
    }
}

void copyarr(int from[N], int to[N]) {
    for (int i=0; i<N; i++) {
        to[i]=from[i];
    }
}

void set1(int k[N]) {
    set0(k);
    k[0]=1;
}

void set0(int k[N]) {
    for (int i=0; i<N; i++) k[i] = 0;
}