4-6

#include<stdio.h>
double fact(int n);
int main(void)
{
    int i;
    double sum;
    sum=0;
    for(i=1;i<=100;i++)
        sum=sum+fact(i);
    printf("1!+2!+...+100!=%e\n",sum);

    return 0;
}
    double fact(int n)
    {
        int i;
        double result;

        result=1;
        for(i=1;i<=n;i++)
            result=result*i;
        return result;
}