Submission #20080

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
20080	2016-02-25T10:39:15 Z	sui	Σ (kriii4_P2)	C++14	100 / 100	19 ms	1884 KB

P2

#define _CRT_SECURE_NO_WARNINGS // scanf(), gets() (needed for Visual C++)

//#define NDEBUG
#include <cassert>

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <functional>
#include <string>
#include <vector>

#include <queue>
#include <set>
#include <map>
#include <unordered_map>
#include <stack>
#include <deque>

using namespace std;

#define MEMSET(x, WITH) memset(x, (WITH), sizeof(x))
#define FOR(i, E) for(int i=0; i<(E); i++)
#define REP(i, LO, HI) for(int i=(LO); i<=(HI); i++)

#define GETINT(x) scanf("%d", &x)
#define GETDBL(x) scanf("%lf", &x)
#define GETSTR(x) scanf("%s", x)
#define NEWINT(x) int x; scanf("%d", &x)
#define NEWDBL(x) double x; scanf("%lf", &x)
#define NEWLN putchar('\n')

#ifdef _WIN32
#define popcnt __popcnt
#else
#define popcnt __builtin_popcount
#endif

typedef long long ll;
//const ll MOD = 1000000007;
//const double PI = atan(1) * 4;







const ll MOD = 1000000007;

ll powerMod(ll a, ll n) {
	ll ans = 1;
	for (int i=62; i>=0; i--) {
		ans = ans * ans % MOD;
		if ((n>>i)&1)
			ans = ans * a % MOD;
	}
	return ans;
}


ll a[10333];
ll b[10333];
ll ans;

int main() {
	int M; cin >> M;
	FOR(i, M) cin >> b[i] >> a[i];



	ll denom = 1;
	FOR(i, M) denom = denom * b[i] % MOD;
	
	ll numer = 0;
	FOR(i, M) {
		ll n = a[i] * denom % MOD * powerMod(b[i], MOD-2) % MOD;
		
		numer = (numer + n) % MOD;
	}


	ans = numer * powerMod(denom, MOD-2) % MOD;
	cout << ans << endl;
	


	/*
	ans = 0;
	FOR(i, M) {
		ll term = a[i] * powerMod(b[i], MOD-2) % MOD;
		ans += term;
		ans %= MOD;
	}
	cout << ans << endl;
	*/


	return 0;
}

Subtask #1

100.0 / 100.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	19 ms	1884 KB	Output is correct
2	Correct	14 ms	1884 KB	Output is correct
3	Correct	17 ms	1884 KB	Output is correct
4	Correct	9 ms	1884 KB	Output is correct
5	Correct	15 ms	1884 KB	Output is correct
6	Correct	11 ms	1884 KB	Output is correct
7	Correct	14 ms	1884 KB	Output is correct
8	Correct	14 ms	1884 KB	Output is correct
9	Correct	19 ms	1884 KB	Output is correct
10	Correct	15 ms	1884 KB	Output is correct
11	Correct	18 ms	1884 KB	Output is correct
12	Correct	18 ms	1884 KB	Output is correct
13	Correct	14 ms	1884 KB	Output is correct
14	Correct	19 ms	1884 KB	Output is correct
15	Correct	15 ms	1884 KB	Output is correct
16	Correct	12 ms	1884 KB	Output is correct
17	Correct	13 ms	1884 KB	Output is correct
18	Correct	16 ms	1884 KB	Output is correct
19	Correct	19 ms	1884 KB	Output is correct
20	Correct	13 ms	1884 KB	Output is correct