#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define rd_init() char*rp=({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define rd_skip() while(*rp++>=48)
#define rd() ({int _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) ({ulong _z=v;do*--wp=_z%10+48;while(_z/=10);})
#define wt1(v) ({char wbuf[64],*wp=wbuf+sizeof wbuf;wt(v);write(1,wp,wbuf+sizeof wbuf-wp);})
#define rep(v,e) for(typeof(e) v=0;v<e;++v)
#define rrep(v,e) for(typeof(e) v=e;v--;)

typedef unsigned long ulong;

int t1[50000];
int t5[50000];

int main(){
	rd_init();
	rd_skip();
	int m=rd();
	int z=0;
	int t2=0;
	int t3=0;
	int s=*rp++&1;
	int l=0;
	for(int c;c=*rp++,c!='\n';){
		if(c=='-'){
			++l;
		}else{
			c&=1;
			int d=s+c;
			if(d&2){
				if(l&1){
					t1[l>>1]+=1;
				}else{
					t2+=l>>1;
				}
			}else if(d&1){
				t2+=l>>1;
				t3+=l&1;
			}else if(l){
				t5[l+1>>1]+=1;
				t3+=~l&1;
			}
			z+=c;
			s=c;
			l=0;
		}
	}
	rep(i,50000){
		rrep(j,t1[i]){
			if(m<i){
				z+=m*2;
				goto owari;
			}
			z+=i*2+1;
			m-=i;
		}
	}
	if(m<t2){
		z+=m*2;
		goto owari;
	}
	z+=t2*2;
	m-=t2;
	rrep(i,50000){
		rrep(j,t5[i]){
			if(m<i){
				z+=m?m*2-1:0;
				goto owari;
			}
			z+=i*2-1;
			m-=i;
		}
	}
	if(m<t3){
		z+=m;
		goto owari;
	}
	z+=t3;

	owari:;
	wt1(z);
	_exit(0);
}