#include<stdio.h>
#include<stdlib.h>
/*定义数组的最大位数*/
#define MAXARRAY 1000
int main()
{
    int fac[MAXARRAY],add[MAXARRAY];
    int top,n,i,j;
    char ch;
    clrscr();
    while(1)
    {
        /*输入要计算的整数*/
        while(1)
        {
            printf("Please input the integer to compute:\n");
            scanf("%d",&n);
            if(n<0)
            {
                printf("Please input an integer greater -1\n");
                continue;
            }
            else
                break;
        }
        /*初始化结果数组和进位数组*/
        fac[0]=1;
        add[0]=0;
        for(j=1;j<=MAXARRAY-1;j++)
        {
            fac[j]=0;
            add[j]=0;
        }
        top=0;
        for(i=1;i<=n;i++)
        {
            /*计算进位数组add*/
            for(j=0;j<=top;j++)
            {
                fac[j]=fac[j]*i;
                if(j==0)
                    add[j]=fac[j]/10;
                else
                    add[j]=(fac[j]+add[j-1])/10;
            }
            /*更新top的值*/
            if(add[top]>=1)
                top++;
            /*计算结果数组fac*/
            for(j=0;j<=top;j++)
            {
                if(j==0)
                    fac[j]=fac[j]%10;
                else
                    fac[j]=(fac[j]+add[j-1])%10;
            }
        }
        /*输出结果数组fac*/
        printf("\n%d!=",n);
        for(j=top;j>=0;j--)
        {
            printf("%d",fac[j]);
        }
        printf("\n\n");
        printf("Please input 'c' to continue.\n");
        ch=getch();
        if(ch!='c')
            break;
    }
    return 0;
}