func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MAXN = 200020;   const int MOD = 1000000000;   int add(int a, int b) { return a >= MOD - b ? a - MOD + b : a + b; }   int mul(int a, int b) {     return a ? (b < MOD / a ? a * b : (long long)a * b % MOD) : 0;   }   int sub(int a, int b) { return a < b ? a - b + MOD : a - b; }   template <int MATRIX_MAXN = 2>   struct Matrix {     int n;     int mat[MATRIX_MAXN][MATRIX_MAXN];     void initEyeMatrix() {       n = 2;       mat[0][0] = 1;       mat[0][1] = 0;       mat[1][0] = 0;       mat[1][1] = 1;     }     void initFibMatrix() {       n = 2;       mat[0][0] = 0;       mat[0][1] = 1;       mat[1][0] = 1;       mat[1][1] = 1;     }     Matrix operator*(const Matrix &rhs) const {       Matrix res;       res.n = n;       for (int i = 0; i < n; i++) {         for (int j = 0; j < n; j++) {           res.mat[i][j] = 0;           for (int k = 0; k < n; k++) {             res.mat[i][j] = add(res.mat[i][j], mul(mat[i][k], rhs.mat[k][j]));           }         }       }       return res;     }   };   int fibsum[MAXN], a[MAXN];   Matrix<> fibmat[MAXN];   void initFibsum() {     fibsum[0] = fibsum[1] = 1;     fibmat[0].initEyeMatrix();     Matrix<> fmat;     fmat.initFibMatrix();     for (int i = (2); i < (MAXN); i++)       fibsum[i] = add(fibsum[i - 1], fibsum[i - 2]);     for (int i = (1); i < (MAXN); i++) {       fibmat[i] = fibmat[i - 1] * fmat;       fibsum[i] = add(fibsum[i - 1], fibsum[i]);     }   }   int getFib(int n, int f0, int f1) {     return add(mul(f0, fibmat[n].mat[0][0]), mul(f1, fibmat[n].mat[1][0]));   }   struct Segment {     int f0, f1, delta, size;     Segment(int f0 = 0, int f1 = 0, int delta = 0, int size = 0)         : f0(f0), f1(f1), delta(delta), size(size) {}     int getF0() const { return add(f0, mul(delta, fibsum[size - 1])); }     int getF1() const { return add(f1, mul(delta, sub(fibsum[size], 1))); }     Segment operator+(const Segment &rhs) const {       return Segment(add(getF0(), getFib(size, rhs.getF0(), rhs.getF1())),                      add(getF1(), getFib(size + 1, rhs.getF0(), rhs.getF1())), 0,                      size + rhs.size);     }   };   template <int MAXN = 200020, int MAXNODE = MAXN << 2>   struct SegmentTree {     int n;     Segment seg[MAXNODE];     static int LEFT(int idx) { return idx << 1; }     static int RIGHT(int idx) { return (idx << 1) | 1; }     void _build(int idx, int lower, int upper) {       if (lower == upper) {         seg[idx] = Segment(a[lower], a[lower], 0, 1);         return;       }       int middle = (lower + upper) >> 1;       _build(LEFT(idx), lower, middle);       _build(RIGHT(idx), middle + 1, upper);       seg[idx] = seg[LEFT(idx)] + seg[RIGHT(idx)];     }     void init(int n) {       this->n = n;       _build(1, 0, n - 1);     }     void pushDown(int idx) {       seg[LEFT(idx)].delta = add(seg[LEFT(idx)].delta, seg[idx].delta);       seg[RIGHT(idx)].delta = add(seg[RIGHT(idx)].delta, seg[idx].delta);       seg[idx].delta = 0;     }     int l, r, x, v;     void _modify(int idx, int lower, int upper) {       if (l <= lower && upper <= r) {         seg[idx].delta = add(seg[idx].delta, v);         return;       }       pushDown(idx);       int middle = (lower + upper) >> 1;       if (r <= middle) {         _modify(LEFT(idx), lower, middle);       } else if (middle < l) {         _modify(RIGHT(idx), middle + 1, upper);       } else {         _modify(LEFT(idx), lower, middle);         _modify(RIGHT(idx), middle + 1, upper);       }       seg[idx] = seg[LEFT(idx)] + seg[RIGHT(idx)];     }     void modify(int l, int r, int v) {       this->l = l;       this->r = r;       this->v = v;       _modify(1, 0, n - 1);     }     void _assign(int idx, int lower, int upper) {       if (lower == upper) {         seg[idx] = Segment(v, v, 0, 1);         return;       }       pushDown(idx);       int middle = (lower + upper) >> 1;       if (x <= middle) {         _assign(LEFT(idx), lower, middle);       } else {         _assign(RIGHT(idx), middle + 1, upper);       }       seg[idx] = seg[LEFT(idx)] + seg[RIGHT(idx)];     }     void assign(int x, int v) {       this->x = x;       this->v = v;       _assign(1, 0, n - 1);     }     Segment _calc(int idx, int lower, int upper) {       if (l <= lower && upper <= r) return seg[idx];       pushDown(idx);       int middle = (lower + upper) >> 1;       Segment res;       if (r <= middle) {         res = _calc(LEFT(idx), lower, middle);       } else if (middle < l) {         res = _calc(RIGHT(idx), middle + 1, upper);       } else {         res = _calc(LEFT(idx), lower, middle) +               _calc(RIGHT(idx), middle + 1, upper);       }       seg[idx] = seg[LEFT(idx)] + seg[RIGHT(idx)];       return res;     }     Segment calc(int l, int r) {       this->l = l;       this->r = r;       return _calc(1, 0, n - 1);     }   };   int n, m;   SegmentTree<> smt;   int main() {     initFibsum();     scanf( %d%d , &n, &m);     for (int i = (0); i < (n); i++) scanf( %d , &a[i]);     smt.init(n);     for (int _ = (0); _ < (m); _++) {       int op;       scanf( %d , &op);       if (op == 1) {         int x, v;         scanf( %d%d , &x, &v);         smt.assign(x - 1, v);       } else if (op == 2) {         int l, r;         scanf( %d%d , &l, &r);         printf( %d n , smt.calc(l - 1, r - 1).getF0());       } else {         int l, r, d;         scanf( %d%d%d , &l, &r, &d);         smt.modify(l - 1, r - 1, d);       }     }     return 0;   }   