complete 11401.rs 13171.rs 13172.rs 13977.rs

storage/zeta/rs/completed/13172.rs

@@ -0,0 +1,37 @@
+use std::io::{read_to_string, stdin};
+
+const MOD: usize = 1_000_000_007;
+
+fn get_mod_power(n: usize, p: usize) -> usize {
+    let mut x = p;
+    let mut curr = n % MOD;
+    let mut res = 1;
+    while x > 0 {
+        if x & 1 == 1 {
+            res *= curr;
+            res %= MOD;
+        }
+        x >>= 1;
+        curr *= curr;
+        curr %= MOD;
+    }
+    res
+}
+
+fn main() {
+    let temp = read_to_string(stdin()).unwrap();
+    let mut iter = temp
+        .split_ascii_whitespace()
+        .map(|x| x.parse::<usize>().unwrap());
+    let m = iter.next().unwrap();
+    let dices = (0..m)
+        .map(|_| (iter.next().unwrap(), iter.next().unwrap()))
+        .collect::<Vec<_>>();
+
+    let res = dices
+        .iter()
+        .map(|&(n, s)| s * get_mod_power(n, MOD - 2) % MOD)
+        .sum::<usize>()
+        % MOD;
+    println!("{}", res);
+}