Submission #2840485

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Source Code Expand

#include <cstdio>
#include <algorithm>
using namespace std;
using ll = long long int;

const int S = 1000005;
const int MOD = 998244353;
ll fact[S+10], finv[S+10];

ll mod_pow(ll X, ll N) {
    ll res = 1;
    for(; N>0; N>>=1) {
        if(N & 1) (res *= X) %= MOD;
        (X *= X) %= MOD;
    }
    return res;
}

void comb_init() {
    fact[0] = 1;
    for(int i=1; i<=S; i++) {
        fact[i] = (fact[i-1] * i) % MOD;
    }

    finv[S] = mod_pow(fact[S], MOD-2);
    for(int i=S; i>=1; i--) {
        finv[i-1] = (finv[i] * i) % MOD;
    }
}

ll comb(int n, int r) {
    if(n < 0 || r < 0 || r > n) return 0;
    return fact[n] * finv[n-r] % MOD * finv[r] % MOD;
}

int main() {
    comb_init();
    int N, M; scanf("%d%d", &N, &M);
    if(N < M) swap(N, M);

    ll ans = 0;
    for(int k=1; k<=M; k++) {
        ll pre = comb(2*k, k);
        ll suf = comb(N+M-2*k, N-k);

       (ans += pre * suf % MOD) %= MOD;
    }
    ans = ans * mod_pow(2 * comb(N+M, N) % MOD, MOD - 2) % MOD;
    (ans += N) %= MOD;
    printf("%lld\n", ans);
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:38:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     int N, M; scanf("%d%d", &N, &M);
                                    ^

Judge Result