#include<bits/stdc++.h>
#define ls(k) k << 1
#define rs(k) k << 1 | 1
#define fi first
#define se second
#define open(s1, s2) freopen(s1, "r", stdin), freopen(s2, "w", stdout);
using namespace std;
typedef __int128 __;
typedef long double lb;
typedef double db;
typedef unsigned long long ull;
typedef long long ll;
bool Begin;
const int N = 5e5 + 10, mod = 998244353;
inline ll read(){
    ll x = 0, f = 1;
    char c = getchar();
    while(c < '0' || c > '9'){
        if(c == '-')
          f = -1;
        c = getchar();
    }
    while(c >= '0' && c <= '9'){
        x = (x << 1) + (x << 3) + (c ^ 48);
        c = getchar();
    }
    return x * f;
}
inline void write(ll x){
	if(x < 0){
		putchar('-');
		x = -x;
	}
	if(x > 9)
	  write(x / 10);
	putchar(x % 10 + '0');
}
int Max, n, m, x, ans, inv2, cnt;
int P[N], F[N], phi[N], mu[N], s[N];
bool f[N];
inline int qpow(int a, int b){
	int ans = 1;
	while(b){
		if(b & 1)
		  ans = 1ll * ans * a % mod;
		a = 1ll * a * a % mod;
		b >>= 1;
	}
	return ans;
}
void init(){
	phi[1] = mu[1] = 1;
	for(int i = 2; i <= Max; ++i){
		if(!f[i]){
			P[++cnt] = i;
			mu[i] = -1;
			phi[i] = i - 1;
		}
		for(int j = 1; j <= cnt && 1ll * i * P[j] <= Max; ++j){
			f[i * P[j]] = 1;
			if(i % P[j]){
				phi[i * P[j]] = phi[i] * phi[P[j]];
				mu[i * P[j]] = -mu[i];
			}
			else{
				phi[i * P[j]] = phi[i] * P[j];
				break;
			}
		}
		mu[i] = (mu[i] + mod) % mod;
	}
	for(int d = 1; d <= Max; ++d)
	  for(int n = d; n <= Max; n += d)
	    F[n] = (F[n] + 1ll * (x % d) * mu[n / d] % mod) % mod;
	for(int i = 1; i <= Max; ++i)
	  s[i] = ((1ll * inv2 * phi[i] % mod - F[i] + mod) % mod + s[i - 1]) % mod;
}
bool End;
int main(){
	inv2 = qpow(2, mod - 2);
	n = read(), m = read(), x = read();
	Max = min(n, m);
	ans = (1ll * n * m % mod * x % mod + 1ll * n * m % mod * (n + 1) % mod * (m - 1) % mod * qpow(8, mod - 2) % mod - 1ll * n * m % mod * (m + 1) % mod * qpow(4, mod - 2) % mod + mod) % mod;
	init();
	for(int l = 1, r; l <= Max; l = r + 1){
		r = min(n / (n / l), m / (m / l));
		ans = (ans + 1ll * (n / l) * (m / l) % mod * ((s[r] - s[l - 1] + mod) % mod) % mod) % mod;
	}
	write(ans);
	cerr << '\n' << abs(&Begin - &End) / 1048576 << "MB";
	return 0;
}

 #include<bits/stdc++.h>
#define ls(k) k << 1
#define rs(k) k << 1 | 1
#define fi first
#define se second
#define open(s1, s2) freopen(s1, "r", stdin), freopen(s2, "w", stdout);
using namespace std;
typedef __int128 __;
typedef long double lb;
typedef double db;
typedef unsigned long long ull;
typedef long long ll;
bool Begin;
const int N = 5e5 + 10, mod = 998244353;
inline ll read(){
    ll x = 0, f = 1;
    char c = getchar();
    while(c < '0' || c > '9'){
        if(c == '-')
          f = -1;
        c = getchar();
    }
    while(c >= '0' && c <= '9'){
        x = (x << 1) + (x << 3) + (c ^ 48);
        c = getchar();
    }
    return x * f;
}
inline void write(ll x){
	if(x < 0){
		putchar('-');
		x = -x;
	}
	if(x > 9)
	  write(x / 10);
	putchar(x % 10 + '0');
}
int Max, n, m, x, ans, inv2, cnt;
int P[N], F[N], phi[N], mu[N], s[N];
bool f[N];
inline int qpow(int a, int b){
	int ans = 1;
	while(b){
		if(b & 1)
		  ans = 1ll * ans * a % mod;
		a = 1ll * a * a % mod;
		b >>= 1;
	}
	return ans;
}
void init(){
	phi[1] = mu[1] = 1;
	for(int i = 2; i <= Max; ++i){
		if(!f[i]){
			P[++cnt] = i;
			mu[i] = -1;
			phi[i] = i - 1;
		}
		for(int j = 1; j <= cnt && 1ll * i * P[j] <= Max; ++j){
			f[i * P[j]] = 1;
			if(i % P[j]){
				phi[i * P[j]] = phi[i] * phi[P[j]];
				mu[i * P[j]] = -mu[i];
			}
			else{
				phi[i * P[j]] = phi[i] * P[j];
				break;
			}
		}
		mu[i] = (mu[i] + mod) % mod;
	}
	for(int d = 1; d <= Max; ++d)
	  for(int n = d; n <= Max; n += d)
	    F[n] = (F[n] + 1ll * (x % d) * mu[n / d] % mod) % mod;
	for(int i = 1; i <= Max; ++i)
	  s[i] = ((1ll * inv2 * phi[i] % mod - F[i] + mod) % mod + s[i - 1]) % mod;
}
bool End;
int main(){
	inv2 = qpow(2, mod - 2);
	n = read(), m = read(), x = read();
	Max = min(n, m);
	ans = (1ll * n * m % mod * x % mod + 1ll * n * m % mod * (n + 1) % mod * (m - 1) % mod * qpow(8, mod - 2) % mod - 1ll * n * m % mod * (m + 1) % mod * qpow(4, mod - 2) % mod + mod) % mod;
	init();
	for(int l = 1, r; l <= Max; l = r + 1){
		r = min(n / (n / l), m / (m / l));
		ans = (ans + 1ll * (n / l) * (m / l) % mod * ((s[r] - s[l - 1] + mod) % mod) % mod) % mod;
	}
	write(ans);
	cerr << '\n' << abs(&Begin - &End) / 1048576 << "MB";
	return 0;
}