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

int main() {
    float a=0.5,b=0.5;
    int c,d;
    long int e;
    scanf("%d %d %ld",&c,&d,&e);
    double f=(c*a*e)+(d*b*e);
    double s=((10*10*10*10*10*10*10*10*10)+7);
    int z=fmod(f,s);
    printf("%d",z);/* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}