根据题目所给公式推导出base矩阵为1 1
-1 0，接下来就可以套用快速幂矩阵模板。
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
#include<cstring>
#define ll long long
using namespace std;
const int mo = 1e9 + 7;
struct node{ll m[2][2];};
ll x,y;node cmp(node a, node b){node te;for(int i = 0; i < 2; i++)for(int j = 0; j < 2; j++){te.m[i][j]=0;for(int k = 0; k< 2; k++){te.m[i][j] += a.m[i][k] * b.m[k][j];//；long long防止数据溢出 te.m[i][j] %= mo; }}return te;
}
node powermod(ll n){node ans,base;base.m[0][0] = base.m[0][1] = 1;base.m[1][0] = -1;base.m[1][1] = 0;ans.m[0][0] = y - x;ans.m[1][1] = x; ans.m[0][1] = ans.m[1][0] = y; // ans 初始化为单位矩阵while(n){if(n&1) ans = cmp(ans, base);n >>= 1;base=cmp(base, base);}return ans;}int main(){ll n;node te;scanf("%I64d%I64d%I64d",&x,&y,&n);te = powermod(n-1);ll tt = te.m[1][1];while(tt < 0)tt += mo;printf("%I64d\n", tt);return 0;
}