#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() ({int _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) ({unsigned _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 chmax(v,a) (v=v>=a?v:a)

int a[1002];

int main(){
	rd_init();
	int n=rd();
	int m=rd();
	char*s=rp;
	char*t=rp+n+1;
	rep(y,m){
		int p=0;
		rep(x,n){
			int q=a[x+1];
			p+=1+(s[x]==t[y]);
			chmax(p,a[x]);
			chmax(a[x+1],p);
			p=q;
		}
	}
	wt1(n+m-a[n]);
	_exit(0);
}