65 lines
1.9 KiB
C++
65 lines
1.9 KiB
C++
#include <iostream>
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#include <cstring>
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#include <cstdio>
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#include <algorithm>
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using namespace std;
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const __int64 MAX_N = 5;
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const __int64 MOD = 1000000007;
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__int64 N;
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void multipy( __int64 a[MAX_N][MAX_N], __int64 b[MAX_N][MAX_N], __int64 c[MAX_N][MAX_N] ){
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for( __int64 i = 1; i <= 4; i++ ){
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for( __int64 j = 1; j <= 4; j++ ){
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c[i][j] = 0;
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for( __int64 k = 1; k <= 4; k++ ){
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c[i][j] = ( c[i][j] + a[i][k] * b[k][j] % MOD ) % MOD;
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}
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}
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}
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}
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void get_matrix_pow( __int64 a[MAX_N][MAX_N], __int64 n ){
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__int64 ans[MAX_N][MAX_N] = {0};
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__int64 temp[MAX_N][MAX_N];
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for( __int64 i = 1; i <= 4; i++ ) ans[i][i] = 1;
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while( n ){
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if( n % 2 == 1 ){
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multipy( ans, a, temp );
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memcpy( ans, temp, sizeof( __int64 ) * MAX_N * MAX_ );
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}
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multipy( a, a, temp );
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memcpy( a, temp, sizeof( __int64 ) * MAX_N * MAX_ );
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n /= 2;
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}
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memcpy( a, ans, sizeof( __int64 ) * MAX_N * MAX_ );
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}
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__int64 solve( __int64 n ){
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__int64 a[MAX_N][MAX_N] = {0};
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if( n < 0 ){
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return 0;
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}
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if( n == 0 ){
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return 1;
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}else if( n == 1 ){
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return 2;
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}
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a[1][1] = 0;a[1][2] = 1;a[1][3] = 0;a[1][4] = 0;
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a[2][1] = 0;a[2][2] = 0;a[2][3] = 1;a[2][4] = 0;
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a[3][1] = 1;a[3][2] = 1;a[3][3] = 1;a[3][4] = 0;
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a[4][1] = 0;a[4][2] = 0;a[4][3] = 1;a[4][4] = 1;
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get_matrix_pow( a, n - 1 );
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__int64 ans = 0;
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__int64 b[MAX_N];
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b[1] = b[2] = b[3] = 1;
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b[4] = 2;
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for( __int64 i = 1; i <= 4; i++ ){
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ans = ( ans + a[4][i] * b[i] % MOD ) % MOD;
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}
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return ans;
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}
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int main(){
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__int64 A, B;
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while( scanf( "%I64d%I64d", &A, &B ) != EOF ){
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printf( "%I64d\n", ( solve( B ) - solve( A - 1 ) + MOD ) % MOD );
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}
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return 0;
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}
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