#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
unsigned long long vir(int n)
{
    unsigned long long a;
    a=n;
    const unsigned int M = 1000000007;
    
    a=a%M;
  return a;
}
int main()
{
    int a[3],i,c;
    unsigned long long b;
    for(i=0;i<3;i++)
        {
        scanf("%d",&a[i]);
    }
    c=(a[0]*0.5*a[2]+a[1]*0.5*a[2]);
    b=vir(c);
    printf("%lld",b);
    return 0;
}