#include <stdio.h>
int main() {
	long long n,m,k,s = 0,x,y;

	FILE*in  = fopen("stergeri.in","r");
	FILE*out = fopen("stergeri.out","w");

	fscanf(in, "%ld", &n);
	fscanf(in, "%ld", &m);
	fscanf(in, "%ld", &k);

	for (;k;k--) {
	    fscanf(in, "%ld%ld", &x, &y);
	    s += x+y-1;
	}
	fprintf(out, "%ld", s+k);
	return 0;
}