#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main(){
    unsigned long long int a, b, t, n, n_a, n_b; 
    float rate_a = 0.5;
    float rate_b = 0.5;
    scanf("%llu %llu %llu", &a, &b, &t);

    n_a = rate_a * a * t;
    n_b = rate_b * b * t;
    n = (n_a + n_b) % (10^9 + 7); 
    
    printf("%llu\n", n);

    return 0;
}