tribonacci

Everybody knows Fibonacci numbers, now we are talking about the Tribonacci numbers: 
T[0] = T[1] = T[2] = 1; 
T[n] = T[n - 1] + T[n - 2] + T[n - 3] (n >= 3)

Given a and b, you are asked to calculate the sum from the ath Fibonacci number to the bth Fibonacci number, mod 1,000,000,007, that is (T[a] + T[a + 1] + ... + T[b]) % 1,000,000,007.

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;

;
;

__int64 N;

void multipy( __int64 a[MAX_N][MAX_N], __int64 b[MAX_N][MAX_N], __int64 c[MAX_N][MAX_N] ){
    ; i <= ; i++ ){
        ; j <= ; j++ ){
            c[i][j] = ;
            ; k <= ; k++ ){
                c[i][j] = ( c[i][j] + a[i][k] * b[k][j] % MOD ) % MOD;
            }
        }
    }
}

void get_matrix_pow( __int64 a[MAX_N][MAX_N], __int64 n ){
    __int64 ans[MAX_N][MAX_N] = {};
    __int64 temp[MAX_N][MAX_N];
    ; i <= ; i++ )   ans[i][i] = ;

    while( n ){
         ==  ){
            multipy( ans, a, temp );
            memcpy( ans, temp, sizeof( __int64 ) * MAX_N * MAX_N );
        }
        multipy( a, a, temp );
        memcpy( a, temp, sizeof( __int64 ) * MAX_N * MAX_N );
        n /= ;
    }
    memcpy( a, ans, sizeof( __int64 ) * MAX_N * MAX_N );
}

__int64 solve( __int64 n ){
    __int64 a[MAX_N][MAX_N] = {};
     ){
        ;
    }
     ){
        ;
    } ){
        ;
    }
    a[][] = ;a[][] = ;a[][] = ;a[][] = ;
    a[][] = ;a[][] = ;a[][] = ;a[][] = ;
    a[][] = ;a[][] = ;a[][] = ;a[][] = ;
    a[][] = ;a[][] = ;a[][] = ;a[][] = ;
    get_matrix_pow( a, n -  );
    __int64 ans = ;
    __int64 b[MAX_N];
    b[] = b[] = b[] = ;
    b[] = ;
    ; i <= ; i++ ){
        ans = ( ans + a[][i] * b[i] % MOD ) % MOD;
    }
    return ans;
}

int main(){
    __int64 A, B;
    while( scanf( "%I64d%I64d", &A, &B ) != EOF ){
        printf(  ) + MOD ) % MOD );
    }
    ;
}