import std;
void main(){
	auto a = readln.split.to!(long[]);
	auto N = a[0];
	auto M = a[1];
	long[][] A;
	for(auto n = 0; n < N; n++){
		A ~= readln.split.to!(long[]);
	}
	if(N == 1){
		writeln(0);
		return;
	}
	auto cost = new long[][](N + 1, M);
	for(auto n = 0; n < N; n++){
		long min_cost = cost[n].minElement;
		for(auto m = 0; m < M; m++){
			if(cost[n][m] == min_cost){
				cost[n + 1][m] = min_cost + A[n][m];
			}else{
				cost[n + 1][m] = min(min_cost + A[n][m] + A[n - 1][m], cost[n][m] + A[n][m]);
			}
		}
	}
	//stderr.writeln(cost);
	writeln(cost[$ - 1].minElement);
}