func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, q;   const int N = 2e5 + 10;   const int inf = 1e9;   char s[N];   struct Node {     Node() {       for (int i = 0; i < 5; i++) {         for (int j = 0; j < 5; j++) {           dp[i][j] = (i == j) ? 0 : inf;         }       }     }     int dp[5][5];   };   Node operator*(const Node& u, const Node& v) {     Node ans;     for (int i = 0; i < 5; i++) {       for (int j = 0; j < 5; j++) {         ans.dp[i][j] = inf;         for (int k = 0; k < 5; k++) {           ans.dp[i][j] = min(u.dp[i][k] + v.dp[k][j], ans.dp[i][j]);         }       }     }     return ans;   }   Node nodes[N * 4];   void build_tree(int l, int r, int rt) {     Node& v = nodes[rt];     if (l == r) {       char c = s[l - 1];       if (c ==  2 ) {         v.dp[0][0] = 1;         v.dp[0][1] = 0;       } else if (c ==  0 ) {         v.dp[1][1] = 1;         v.dp[1][2] = 0;       } else if (c ==  1 ) {         v.dp[2][2] = 1;         v.dp[2][3] = 0;       } else if (c ==  7 ) {         v.dp[3][3] = 1;         v.dp[3][4] = 0;       } else if (c ==  6 ) {         v.dp[3][3] = 1;         v.dp[4][4] = 1;       }       return;     }     int m = (l + r) >> 1;     build_tree(l, m, 2 * rt);     build_tree(m + 1, r, 2 * rt + 1);     v = nodes[2 * rt] * nodes[2 * rt + 1];   }   Node query(int L, int R, int l, int r, int rt) {     Node& v = nodes[rt];     if (L <= l && R >= r) return v;     int m = (l + r) >> 1;     bool left = false, right = false;     Node ltemp, rtemp;     if (L <= m) {       ltemp = query(L, R, l, m, rt * 2);       left = true;     }     if (R > m) {       rtemp = query(L, R, m + 1, r, rt * 2 + 1);       right = true;     }     if (left && right) return ltemp * rtemp;     if (left) return ltemp;     if (right) return rtemp;   }   int main() {     scanf( %d %d , &n, &q);     scanf( %s , s);     build_tree(1, n, 1);     for (int i = 0; i < q; i++) {       int l, r;       scanf( %d %d , &l, &r);       Node v = query(l, r, 1, n, 1);       if (v.dp[0][4] == inf)         cout << -1 << endl;       else         cout << v.dp[0][4] << endl;     }     return 0;   }   