hdu3123GCC

The GNU Compiler Collection (usually shortened to GCC) is a compiler system produced by the GNU Project supporting various programming languages. But it doesn’t contains the math operator “!”.
In mathematics the symbol represents the factorial operation. The expression n! means "the product of the integers from 1 to n". For example, 4! (read four factorial) is 4 × 3 × 2 × 1 = 24. (0! is defined as 1, which is a neutral element in multiplication, not multiplied by anything.)
We want you to help us with this formation: (0! + 1! + 2! + 3! + 4! + ... + n!)%m

The first line consists of an integer T, indicating the number of test cases.
Each test on a single consists of two integer n and m.

Output the answer of (0! + 1! + 2! + 3! + 4! + ... + n!)%m.

Constrains
0 < T <= 20
0 <= n < 10^100 (without leading zero)
0 < m < 1000000

#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>

using namespace std;

char s[110000];

int main()
{
    long long t,n,md,a,i,sum,l;
    cin>>t;
    while(t--)
    {
        cin>>s>>md;
        l = strlen(s);
        n = 0;
        if(l>7)n = md;
        else
            for(i = 0;i<l;i++)
                n = n*10+s[i]-‘0‘;
        sum = a = 1;
        for(i = 1;i<=n;i++)
        {
            a = (a*i)%md;
            sum = (sum+a)%md;
        }
        sum%=md;
        cout<<sum<<endl;
    }
    return 0;
}