9/5 C: Operations

#include <stdio.h>

int main(){
    int a,b,h;
    scanf("%d%d%d", &a, &b, &h);
    /*
    int area;
    area = (a + b) * h / 2;
    */
    printf("%d", (a+b)*h/2 );
    //printf("%d", 321);

    return 0;
}