#include <stdio.h>

int main() {
    int a, b, n, count=0;
    printf("Please input a, b, n: ");
    scanf("%d %d %d", &a, &b, &n);
    for (;n>0;n--) {
        count += a*b;
        a--;
        b--;
    }
    printf("The total number is %d", count);
    return 0;
}