Submission #20078

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
20078	2016-02-25T10:36:48 Z	sui	Σ (kriii4_P2)	C++14	100 / 100	791 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 numer = 0;
	FOR(i, M) {
		ll prod = a[i];
		FOR(j, M) if (i != j) prod = prod * b[j] % MOD;

		numer = (numer + prod) % MOD;
	}

	ll denom = 1;
	FOR(i, M) denom = denom * b[i] % 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	774 ms	1884 KB	Output is correct
2	Correct	781 ms	1884 KB	Output is correct
3	Correct	781 ms	1884 KB	Output is correct
4	Correct	786 ms	1884 KB	Output is correct
5	Correct	790 ms	1884 KB	Output is correct
6	Correct	785 ms	1884 KB	Output is correct
7	Correct	783 ms	1884 KB	Output is correct
8	Correct	780 ms	1884 KB	Output is correct
9	Correct	791 ms	1884 KB	Output is correct
10	Correct	789 ms	1884 KB	Output is correct
11	Correct	789 ms	1884 KB	Output is correct
12	Correct	785 ms	1884 KB	Output is correct
13	Correct	779 ms	1884 KB	Output is correct
14	Correct	782 ms	1884 KB	Output is correct
15	Correct	784 ms	1884 KB	Output is correct
16	Correct	788 ms	1884 KB	Output is correct
17	Correct	791 ms	1884 KB	Output is correct
18	Correct	783 ms	1884 KB	Output is correct
19	Correct	780 ms	1884 KB	Output is correct
20	Correct	778 ms	1884 KB	Output is correct