#include<bits/stdc++.h>
#define int long long
#define N 200007
#pragma GCC optimize(2)
using namespace std;
int H,M,A;
int gcd(int a,int b)
{
    return b==0?a:gcd(b,a%b);
}
int zc(int a,int b,int c)
{
    int g=gcd(a,c),x=((b%c+c)%c)%g;
    int t=(c-1-x)/g;
    if(x==0)
    {
        return c/(t+1);
    }
    return 0;
}
int cal1(int a,int b,int c)
{
    int g=gcd(a,c),x=((b%c+c)%c)%g;
    int t=(c-1-x)/g;
    int ans=(x+x+t*g)*(t+1)/2*(c/(t+1));
    return ans;
}
int cal2(int a,int b,int c)
{
    return (b+(c-1)*a+b)*c/2;
}
int down(int a,int b,int c)
{
    return (cal2(a,b,c)-cal1(a,b,c))/c;
}
int up(int a,int b,int c)
{
    return (cal2(a,b,c)+c*(c-zc(a,b,c))-cal1(a,b,c))/c;
}
void solve()
{
    scanf("%lld%lld%lld",&H,&M,&A);
    int ans=down(H*M,A,H-1)-up(H*M,-A,H-1)+(H-1);
    printf("%lld\n",ans);
}
signed main()
{
    solve();
    return 0;
}